Prophecy: I'll bet the United States can support several times it's GDP in debt. Once the creditors start calling, we'll ignore them for several decades saying that we can't pay right now but if they don't want a world financial collapse, they better wait. After waiting and the debt climbing higher, we'll just pretend we never borrowed the money and stick our middle finger at China... probably will result in some kind of world financial collapse, but it'll recover somehow.
So no, the US will never go bankrupt. We'll rewrite history so that we never borrowed the money.