Interest on debt
In 2022, the interest payment for the national debt is expected to be over $500 Billion. This is interest paid to public holders of the debt; it doesn't include about $230 Billion in Intergovernmental debt holdings.
Think of what $500 Billion a year could pay for. According to the Department of Housing and Urban Development, it would cost only $20 billion to end homelessness in the United States. Providing free lunches for all school children up to grade 8 would cost about $30 Billion yearly.
It's been suggested by notable economist Paul Krugman that three to four percent of GDP is actually a low rate for a county to pay. While that may be true, how many countries have a debt as high as the United States?