Its completely unsustainable. It will never be repaid. That’s 100% certain.
Don’t ask me though if it will be a total debt collapse/abrogation, or bouts of hyper-inflation which turns that old debt (and lots of new debt) into worthless paper
I suspect it will be the later, defined by cycles of debt collapse, and then hurried money printing to re-inflate.
That, unfortunately, will cement tyranny in place in the USA as “central planners” go from pillar-to-post claiming to solve the problem while centralizing their power.
An outright collapse, ala the Soviet Union, would be much better
Debt can be renegotiated to a certain degree, but you’ll most likely get some form of money & wealth “evaporation.” Which will lead to tough times” for many people.
We could be entering an economic cycle more like the 1921-1938 time period as the post WW2 inflationary business cycle loses steam.
Hard to tell, history can’t repeat itself, it’s physically impossible, but there can be similarities.
The U.S. debt, and every other National debt will all be forgiven. The catch is that a global currency will need to be adopted and sovereignty surrendered.