There is no national debt, just deficit spending. Congress owes this money to themselves in a sense. The national debt is just a tool that politicians use to convince people that they need to pay more taxes to pay off the debt, in the same sense that normal people have to pay off their debts or sell their not paid for property to then become financially secure.

Congress can just declare the debt paid in a day. It's not even practical to pay off this debt anyway because there is a limit on how much currency exists to begin with. If you add up all the private debt as well it's not possible to pay off the debt because the money used to pay the debt is also on loan. The actual amount of original gold backed money that wasn't loaned out is so small that it wouldn't come anywhere close to paying off all the money loaned out by the US fractional reserve system.

Deficit spending is a problem because it weakens the currency. If people realized this and didn't put their savings in to USD then that would force the government to not spend so much.