I may be incorrect, but it seems to me that the US currency will ultimately back that. If the government does not have the ability to pay, then it will have to

I may be incorrect, but it seems to me that the US currency will ultimately back that. If the government does not have the ability to pay, then it will have to print money to cover the difference, devaluing the currency. It's probably a reasonable position, but it seems to me to be vulnerable to poor timing. For example, if there is a debt crisis, you may have to raise interest rates at exactly the time when you don't want to. When I see very high prices for houses (in relation to salaries), an aging population, and a pension system that can demand money from the government at will... it makes me a bit nervous.