The only bad thing with USD based stable coin is you have to trust that the USA will keep paying its debts longer than you hold the stable coin.

The US has no reason not to pay its debts. Its debts AFAIK are USD denominated. How often has a country defaulted on debt in its own currency? I can think of one example and I thought it was a stupid thing to do at the time (it was forced by creditors, presumably as a punishment) and it was not a complete default, but a haircut.

That sounds like a good bet.