The problem is the fundamentals. The US will "never default on its debt" because it issues debt in its own currency, which it can control the creation of necessary to service that debt (money printer go brrrr).

So nobody is ever concerned about debt; you just say screw it let someone else worry about it, usually future generations. The value has to come from somewhere, and in this case its from the debasement of the dollar.

They defaulted when they stopped honoring gold backing, which was the debt against the legal tender.

Which the feds can always do since they can issue money.

The relevant question is can the US continue producing goods and services that are desirable on a global scale, one of which is a trustworthy society where you can mostly depend on the judicial system keeping things in order, for better or for worse.

And more importantly will others keep accepting USD. Or will they expect to be settled in something else be it other currency or some commodity. If others start to want something else than USD things can go sideways.