From this wiki page we can clearly see that US national debt is growing steadily after 2010 and now it's larger than US GDP already (at the end of 2019).
Still it's commonly believed the debt is maintainable. At least, neither the Obama administration nor the Trump administration care to spend (enough) effort to eliminate the debt.
To overly simplify, the absolute death sentence to this debt problem is that the whole government budget is not enough to pay the interest, but I suppose the actual critical point arrives much earlier than that.
Regarding US debt problem today, the only referenceable example of to me is Hyperinflation in the Weimar Republic . Yet they are only remotely parallel: Weimar Republic back then was hardly a major world power (politically and economically) while US being today's only global hegemony, let alone its Petrodollar policy and other global influence.
So I wonder, being such super power, what would happen to US domestic economy along the debt growing towards such critical point?
To make this question simpler, let's assume that during such progress
- There is no war between US and the other major powers against each other.
- The external force disturbing US policy remains minimal.