Why should the US pay off its debt?
That's a big question. Fortunately I'm not an economist so I don't have to provide you with a big answer.
Well, for the same reasons why people should pay off their credit card debts/mortgages/student loans. Every year a certain amount of the country's surplus (something the US hasn't had since the Republicans came into power) towards the debt. Kind of like minimum payments on credit cards. There's also interest.
So as a tax payer I would be very concerned about my money going into pay interest on my country's debt. That money could be used towards education, health care, research and development, etc...
The fact is that the world is losing faith in the American dollar. The Canadian dollar is above par with the American dollar. EBay is looking pretty sweet now.
The reason for this is because Canada has been paying off our debt yearly for 13 years. It's called running good finances and other countries see this and invest in our economy. The US has managed to convince the world that the US dollar is the most stable currency, however, the longer the US continues to falter in regards to it's national debt the less faith nations will have in their currency. I wouldn't be surprised if the Euro becomes the world's standard currency.