If you're betting on governments you can do worse than the US. The absolute number of debt is scary, but do you doubt we'll be able to pay back our dues?
Essentially the US is riding on its reputation, but as good as that reputation is, as debt continues to raise relative to GDP international banks may grow wary of loaning, or simply want to diversify if they have a lot tied into US bound debt.
That being said, inflation has been relatively mild of late such that a little extra "printing" may not hurt much this time. I just don't like printing as a general fix.
Of course, an actual default for a country like the U.S. is a very unlikely outcome for a variety of reasons. What is more likely, is that inflation is allowed to rise and 'eat' up the debt. The "hope" is that a mild rate of inflation is sufficient to do so. I doubt it though, there have always been periods of high inflation, and there is no reason to think they will not return.