If the debt is in US dollars (which it is) then they actually owe less in real terms.
Thats the easy way to pay off debt - you owe $1 trillion than all you have to do is inflate your currency so much that $1 trillion buys you a loaf of bread. Sell a loaf of bread and then pay off all your debts!
The losers are the holders of that debt - thats why I'd be moving out of US treasuries into gold or other assets.
Thats a simple analogy but close to what the US are trying to acheive.
A rising currency is the baddie - you need to sell more and more just to pay off the same amount of debt.
