It is true that the USD is relatively stable not because the USG somehow "guarantees" its value rather than because the dollar is legal tender in the US.

I disagree. The USD use case as legal tender pales compared to the international markets and what it represents. In the FTX OTC market, for example, about 90% of the $98 trillion in holdings is USD. That is just one example.

There are:

• International debt securities: $45 trillion
• Cross border bank liabilities: $15 trillion
• Official FX reserves: $12 trillion

And that doesnt include the Repo markets or any of the daily transaction activity (which is into tends of trillions daily).