I will answer your question toward the end, following a line formed by stars (which may be invisible).

Facebook is already involved in social engineering and meddling with elections. If you say anything political they don't like, wear political shirts they don't like, run for office on stances they don't like, appear with political speakers they don't like you risk being banned https://www.infowars.com/instagram-bans-researcher-over-pic-with-blacklisted-alex-jones/1 <a href=>. For the dangerous people like Paul Watson, Laura Loomer, and Milo Yiannopolous, Facebook recent had a policy where users could give them death threats as "dangerous individuals" since facebook previously branded them dangerous individual. It is nothing short of Facebook using terrorism against conservative speakers.

"
source:Paul Joseph watson.
see also https://dailycaller.com/2019/07/10/facebook-death-threats-policy/

Facebook is also banning people's posts if they support political parties that facebook doesn't like, despite facebook claiming to hate outside interference in national elections and referendums (such as when they blocked pro-life ads from airing in Ireland-I guess dual citizens can't express a political viewpoint in their home countries).

Facebook previously removed pages representing Britain First in March of last year for breaching community standards. However, the new ban means third-party users may also have their posts removed if they express support for the banned political parties and individuals.
-https://www.ft.com/content/61db0434-61cf-11e9-b285-3acd5d43599e

When states alleged the facebook is in violation of the state's campaign laws, facebook simply points to 47 usc 230 immuity. see page 4, https://www.pdc.wa.gov/sites/default/files/compliance_case_files/47572%20Facebook%2C%20Inc%20%283%29%20Response.pdf

They are also claiming to block foreign interference in elections, but ultimately they get to decide what local and foreign ads, or more precisely, what forms of speech are allowed to be shown....as well as what parties and candidates will have a platform.

What they are doing is depriving people of speech and reason, under fear of the social punishment of ostracism as a means of social engineering to obtain their desired control. Notice that if you allegedly violated a facebook TOS, it simply isn't a deletion-they ban you for a week or more and that is specifically to make you feel it. You risk losing your ability to discuss business matters, you miss opportunities to give birthday wishes, and often these bans occur often when you are engaged in a political debate based upon other content posted, weeks, months, or even years ago. In evolutionary biology ostracism is very painful, and in animal models it often causes the death of the individual. It was the punishment that Ancient Athens practiced instead of delivering the death penalty. In terms of remembered pain, the pain of ostracism is worse than remembered physical pain. Depriving people of speech and reason is to deprive men of Logos, which is the same as reducing people to mere animals.

The death blow of individualism at least as they view things is about control. How it is actually playing out is people are <a href="https://www.marketplace.org/2019/03/06/tech/exclusive-look-numbers-showing-users-leaving-facebook-by-the-millions/>leaving facebook and using it less as the peaceful remedy of dealing with the dictator. They don't have the level of control they desire yet.

As I think congressman Duffy pointed our, there are concerns that facebook's libra if it becomes a global standard, would be used to mimick China's social value score system. Unlike traditional fiat which can be passed person to person, with KYC facebook will know the user behind the digital addresses. because they maintain control of the database, they can determine what a person can and cannot do with libra. In many ways, Facebook will be acting as if they were a government restricting our ability to exchange our property which is the same thing as restricting our liberties. They can expel us from the market altogether if we express views they don't like, just as many of the companies have done to conservative speakers. Many of Libra's partners have explicitly banned conservatives. here is an article a few months old about the companies that have banned people based upon their politics (not sure why they included Zimmerman or others in their list): https://www.businessinsider.com/china-social-credit-system-punishments-and-rewards-explained-2018-4
among them (and countries too) include:
Facebook, Instagram, Twitter, YouTube, the nation of Australia, PayPal, Venmo, GoFundMe, Uber, Uber Eats, Lyft, Medium, TeeSpring, Chase Bank, Eventbrite, Shopify, Patreon, Coinbase, Periscope, Mailchimp,

The list excludes mastercard, but the daily called certain named them [and visa] in discriminating against conservative organizations. https://dailycaller.com/2018/09/04/mastercard-conservative-nonprofits/

You'll notice that some of these are on the same colibra members lists as reported by cryptopolitan https://www.cryptopolitan.com/mark-zucerberg-reveals-all-27-companies-backing-libra-calibra-launched/ and I added some further notes, mostly from wikipedia entries:

Women’s World Banking (overseas banking to poor women)
Kiva (sending money overseas to poor countries)
Booking Holdings (travel (mostly travel search sites))
Andressen Horowitz (investor/enabler of many silicon valley projects, facebook/twitter/github/coinbase/skype/lyft/oculus vr/cryptokitties/arbnb/buzzfeed/coinbase. Gives to to republican congressmen and liberal candidates like bernia sanders, but also gives extensive amounts to democratic presidential candidates including Obama and Clinton.)
Farfetch (london fashion, chinese own a stake)
Iliad (A european telecom, also owns free who created freebox)
Mastercard
Uber
PayU (euroupean payment processor, owned by naspers [name relates to South Africa's nationalist party]-a south African Internet group-which also owns tencent-a chinese internet firm, also invested in swiggy which is an Indian food company. Naspers also owns Myriad International Holdings which is was a major Russian investor in facebook. )
Mercado pago (latin and south America payment processor)
Coinbase
PayPal
Creative3 (sounds like an australian based e3)
Bison Trails (obscure block chain company, but reportedly they had to have a billion bucks to be a member of calibra; current owner was previously a leader of Etsy, another worked at etsy and was founder of grand street (purchased by etsy). Etsy integrates their user stores onto facebook. there is also reports of discrimination against conservatives or mockery of English politics and jihadists )
Calibra
Mercy Corps (this oone should be investigated further, it is a portland orgeon (home of rose city antifa) based company (Their physical location is also within the geographic area covered by rose city antifa)) that has formed partnerships with < href="https://en.wikipedia.org/wiki/Gorilla_FC">antifa groups, that is reportedly funded by George Soros, that provides aid to people in poor countries [my spidey senses are tingling about the mercy corp about the democratic republic of Congo, and the mass immigration to the US from there with people with rolls of $100 bills-and also tingling abut other matters])
Vodafone
United Square Ventures (Also known as union square ventures. venture capitalist: invested in Zynga, twitter, and etsy, and coinbase. )
Ribbit Capital [ also participated with raising 25 million for coinbase with union square ventures, and Andreesen Horowitz. Also invested in Xapo)
Thrive Capital (invested in instagram, sold to facebook. Also invested in twitch and Github) Owner Joshua Kushner is the brother of President Trump's son in Law Jared Kushner. Joshua is also married to Karlie Kloss who is a pro-baby killing feminist)
Visa
Lyft
Stripe(SF based etailing solutions company and payment processor [initial investors included : Peter Thiel, Sequoia Capital, and Andreessen Horowitz.])
Ebay
Spotify
Anchorage (crypto holder, funded by Andreessen Horowitz)
Xapo (hong Kong [aka china] based company that provides bitcoin wallets and crypto vault. Also has a US HQ in delaware. Originally based in Argentina, they moved to pala alto (facebooks area), then later to Switzerland [where Libra is going to be]. Funded by Ribbit)
Breakthrough Innovations (no information found)
and Facebook.

Despite there said to be 28 different companies (and there are many more now), many of them have a lot of things in common-besides discriminating against conservative. The American ones have quite a bit in common. Some of the groups highlight an interest to help move the wealth out of America. Mercy Corps has a link to Soros and domestic terrorism.

So adding on top of the censorship of conservative speakers, there is also an issue of redistribution of America's wealth abroad and exuberant consumption. So long as their assets are backed by securities, could consume whatever they want, while still maintaining liquidity, by minting more assets. Like Gold (except to numismatics), most people never see or hold their gold-they just own/trade gold certificates. Some people lose their crypto keys, others will die without others to inherit their security backed libra-although being centralized platform, that may be possible to recover it.
Subject to Swiss law, They do not need to keep a large percentage of their assets as fiat. If they do not maintain enough liquidity, and they are not able to flip real estate for at least break even, it may trigger Calibra to go off the stable coin model-Just as we seen with our own federal reserve when they ended the Gold standard, and later Tether when a third party couldn't return their assets. Reportedly the Romans devalued their money over time as well.
Because of the social justice interest of these groups, they may chose to do away with the stable coin once it becomes a standard. They may feel it is their duty to empower the rest of the world through redistributing the wealth. That would make holding Libra very dangerous. A capacitor charging America's wealth up, then discharging it to give that wealth to the rest of the world.

As to the need for USA dollars, I do not think that would last long-an additional reason to escape from the stable coin model. One could say it doesn't earn interest in a bank, but people could put their libra into a money market fund. It would ultimately reduce the demand for the US dollar, and would tend to devalue the dollar. The Dollar too has its own risks, particularly with the national debt. If they end up controlling the market then the dollar may be phased out as irrelevant, as will governments the world over, and the world marketplace will be under control of their rules and ambitions. Although people can buy real estate with crypto, and some shops are supporting apps that allows people to pay with bitcoin and altcoins, for the most part that is like a capacitor that charges and discharges randomly or marketing gimmicks. Crypto has yet to have a truly meaningful impact in consumer spending yet in the US, aside the equivalent of making a bunch of people lottery winners who held from the earlier years.

What's different about Libra from other traditional reserve currencies are the people who back it; Those who have the gold make the rules. They could algorithmicly devastate a local population through algorithmic economic sanctions as a virtual condemnation of land without any adversarial hearing to just to acquire the land, infrastructure, resources, even labor dirt cheap, blocking all competitive offers-much worse than the eminent domain practices in the states. You have no rights, you are but an animal who they decide what rewards you get to have in life, and how you get treated by others. As flawed as our country has become through mostly the democrats, we still have a limited means of correcting the problem at the polls or [peaceully speaking] the option to leave, and even though the judges are half educated these days we still enforce our constitutional procedural rights to protect our natural rights half the time from invasive sovereigns-like what these companies are hoping to be. Instead we are dealing with proven despots behind this coin who intend for global control of the marketplace and our rights, they will have chinese styled social control over the users, they have embraced violent Antifa, and they have openly invited incitement of violence against conservatives.

The major difference between the US dollar and the facebook Libra, isn't a matter that many of us are using it as a utility to pay off our debts. Of course, how are debts accumulated? Usually with Fiat. There are hints that there is going to be banking with libra, although Calibra denies that it will be by them. Perhaps it will be done through mastercard here, euroup, and with Xapo in asia, marcado pago in latin and south America, and womans bank, nasper, and kiva in Africa. There may not be the historical jewish practice of jubilee by mastercard as is currently done in America, but maybe the others will be more forgiving given the nature of SJWs. I see no reason why Calibra, since they control the database, can't force someone to pay a debt payment to their partners over their rent, bus fare, or food, once calibra gets the control they desire. Maybe they will be like a jail where you qualify for indigency if your account is below a certain value if they feel compassionate. The libra has a hidden tax, it robs people of their humanity, it robs them of their freedom, it robs them of their speech, it robs them of their ability to use reason, it robs them of their fair trial rights, it robs them of their gun rights, it forced people to bow down before the Gods of the Algorithm, and it ultimately deprives men of their souls. And that just ignores whatever military arm they might come up with. And it is harder to run away from.

One thing I also just now noticed (I saw it I think yesterday on the "zuck buck") is that libra uses the same symbol as steem, only rotated 90 degrees.

source: https://calibra.com/