Let's pretend Yang is right for a second.

GDP in the US is 21 trillion at current estimates. There are all kinds of issues with the way GDP is calculated, but it's at least in the ballpark. So a 10% VAT would shift roughly 2 trillion into the freedom tax (Orwell much?).

So maybe the math kind of pencils out, plus or minus 10 percentage points or so.

Stipulate all that.

What is the actual effect?

Money is transferred. This is the entire point of the system. Some people end up with a net loss, some people end up with a net gain under this system. The trick to making it popular is that the number of people with the net loss is smaller than the number of people with the net gain.

Total purchases of goods and services are down. This is simple enough. When a tax is imposed on something, it becomes more expensive. Demand goes down. Some marginal number of businesses and employees are out of work. The rest are just poorer than they would be otherwise.

For the people with a net gain under the system (assuming they kept their jobs), where does the money go? With overall business activity down, those that remain end up charging more. Chances are, all that windfall will mostly go towards the same basics that are already being paid for like rent, food, gas/energy, childcare, and so on.

When all the dust settles, a few people might be better off at the expense of everyone else and the total result is we are all worse off.