Nothing is immune to the ebb and flow of time. Empires come and Empires fall. From a 50,000 ft level, the US acts like all the other historical empires. Eventually, it will need to cede it's scepter to the next empire.
The good news is ... in most of the cases, nothing really changes for the common folks when the changeover occurs. The common life remains common.
Yes, the debt we're in will be a tough one to rectify without some kind of a reset! I was looking into life for the average Roman just after the fall and it was interesting. De-urbanization happened pretty quickly then came rapid breakdown in education and technology. Most people emptied out of the cities to the countryside and lived that way for centuries. That's probably exactly how it would play out here. Cities would be lawless/dangerous.