Yeah, but as soon as the United States ceases to exist that "willingness" would be gone probably even before it happened, and stay that way for a century or more.
(Not so with US issued silver or gold coins.)
ML/NJ
Probably not. Just look at how popular dollars are in the third world. You think any of them give a damn about the existence of the US? What matters is other people will take them. The history of currency is the history of the masses willingness to accept a transitional product in barter. Issuers, governments, none of that matters. Look up the history of counterfeit British coppers. People were willing to take money they KNEW was counterfeit, for a lower value than the real thing, but still willing to take it in trade, and spend it. The counterfeits were so popular that THEY got counterfeited. There developed a whole layers value system: real coppers, high end fake coppers, lower end fakes, it was wild. Government’s got nothing to do with it. People decide what money they’ll take, and it’s based on their ability to give it to others.