With this level of debt and with this trouble our economy is in the question "will we go bust" turns into "when will we go bust".
What will happen then? I'm too scared to even try to predict.
It's not going to happen, at least not the way most people would envision it. Here is something you might not be aware of. 60% of the national debt is owed to the public, both here an abroad. The government owes 40% of debt to itself, via loans between agencies. So it's not like the bank is going foreclose. Remember the treasury can always create more money which of course causes another set of problems.
As the US debt rises as percent of GNP in relation to the debt of other nations, those who loan money to the government, mostly buyers of treasury bills will demand a higher rate of interest. This will force up interest rates which tends to depress business. Also foreign investors become concerned about the risk of investing in the US. This will cause the dollar to devalue making foreign goods more expensive. These two event will result in an increase in inflation plus a depressed business climate.
In short, the government never goes belly up, but the public suffers a decline in purchasing power of dollar and waves of recession. All which leads to a decline in our standard living.