Debbie, they can always make payments on social security.
WE (when I say we I mean our beloved US Government) PRINT THE MONEY!!!
Even the Swiss, those magnificent people, have essentially gotten hammered loosely linking their currency to gold, so they have almost given up on it.
Paper covers rock!!!
The US Government will never pay back the debt, and will never stop expanding the balance sheet when measured over time. Occasional shrinking of the balance sheet is just for show to fool the people.