The current existence of the National Debt, and also of a non-zero public debt-to-GDP ratio is the inevitable result of a technical decision that Congress has made about how the Treasury should finance its spending. This post talks about that decision, points out that its consequence is the National Debt, and also points out that the very existence of the National Debt is the fault of Congress.)
It is Congress's fault that we have a national debt at this point in our history. And also Congress can largely get rid of this debt over a 10 year period any time it wants to.
The national debt exists today because when the nation went off the Gold Standard in 1971 and adopted its fiat currency system, Congress did not repeal its mandate, very appropriate when our currency was convertible to Gold on demand, in least in theory, requiring that the Government back all its deficit spending with already existing borrowed dollars whose convertibility was covered by our holdings of Gold. This Congressional mandate to borrow funds by issuing debt instruments when the Government deficit spends, is what has caused the national debt to persist.
Had Congress repealed it when President Nixon took the country off the Gold Standard, and had we ceased to issue debt at that time, then the Government would have re-paid all of our 1971 debts as they came due, and our nationaldebt today would be zero and our debt-to-GDP would now be at 0%.