With an annual deficit of $1,000,000,000,000, the government pretends that it will someday have 10 years of $100,000,000,000 surplus to pay the loan back. A government debt of $15,000,000,000,000 requires 150 years of $100,000,000,000 (one hundred billion dollars) of government surpluses to pay off the principles, and this does not include the interest on the debt.
In the Internet bubble years of the Clinton year and the first two years of the 21st century, we had 3 years of $100,000,000,000 surplus (and a fourth surplus less that $100,000,000,000).
The government knows at this time that it will never pay that money back, which is why the throttle is full open. It’s $1,000,000,000,000 in borrowing today, because sometime the rest of the world will change the revolving credit not in the United States’ favor.
(Data source.)