It's simple accounting, as interest payments on the debt become an increasingly higher part of the budget, the end result becomes insolvency. Of course, an act

It's simple accounting, as interest payments on the debt become an increasingly higher part of the budget, the end result becomes insolvency. Of course, an actual default for a country like the U.S. is a very unlikely outcome for a variety of reasons. What is more likely, is that inflation is allowed to rise and 'eat' up the debt. The "hope" is that a mild rate of inflation is sufficient to do so. I doubt it though, there have always been periods of high inflation, and there is no reason to think they will not return.