> The US debt is starting to become an existential problem.

It is not existential except for the financial markets, because they need safe securities: remove US bonds and modern finance grinds to halt.

US debt is high just because the US government decided in the 80s that they will start borrowing money from the rich instead of taxing them. The money exists, and it doesn't have to be borrowed just because Laffer draw a cute curve on a restaurant napkin.