Thinking about your questions(s) — the thing that came to my mind was that by any definition used for a company going belly up, the US government is probably already bankrupt. Bankruptcy is having more obligations (debt) than the resources (assets) to clear the obligations. I do not see the US government filing for bankruptcy or declaring that it will default on its obligations anytime soon.
What is likely to happen is that the debt of the US government will become dammed near worthless through monetizing the debt, which will require or lead to inflation. Really bad inflation. The other possibility is that the interest rate required to get foreign countries to buy our debt is incredibly high, higher or just as high as the standard interest rate on AAA rated debt in 1981 (12%). This will create a situation in which the largest part of the government’s budget is debt servicing (interest payments) and account for virtually all payments made by the taxpayers of the US. This situation will force the government to rewrite the rules for getting federal bucks; expect to hear the phrase “means testing” to appear more and more in the next two decades as it relates to social security and medicare. Also look for states to get less money from DC.
I really do not know what the federal government will do to tame the paper tiger it is creating every budget year — and it may be a while before we see anything profound. It all depends on how much our paper remains worthwhile for the chineese and arab oil sheiks to keep buying. I am throwing out as impossible the other alternative; cutting down federal spending to defense and bare bones government to reduce the debt by running supluses for a decade or four — that will not happen.