$16T in debt is not too bad for a country that owns the world...

$16T in debt is not too bad for a country that owns the world reserve currency, its only 104% of their GDP.
They should be able to go a lot higher, probably around 500% GDP ($80T) before things become a bit tricky.
It will be interesting to see how much they next raise the debt limit, shouldn't waste their time raising it a couple of extra Trillion, just make it say $40T or higher and then they won't have to worry about it for years.

On a more serious note, never underestimate the Yanks, some how they are going to make the rest of the world pay off their debt.