You really want to make a dent in that national debt? (This is rhetorical; I assume you do based on the frequency and tenor of your posts)
Cut the annual budget and create a surplus. Then use that surplus to pay down your debt year after year. But the only way you create a surplus large enough to make meaningful repayments of principal is to institute major spending cuts to social entitlement programs like Medicare/Medicaid and Social Security. By and large, those are programs spent on people in the United States.
https://fiscaldata.treasury.gov/americas-finance-guide/federal-spending/
Look at the top categories from the above link. Net interest (14%) is debt service, which declines as you reduce your national debt and/or interest rates decrease. Other than that, we're talking Social Security (22%), Health (13%), National Defense (13%), Medicare (13%), and Income Security (10%) as the other categories >10%.
Cutting national defense (in your example, pulling the U.S. military out of Europe) could be a portion of that surplus (the cost/benefit analysis of that spending notwithstanding), but it can't all come from there. The most prime places to cut are social security, health/Medicare, and "income security" (welfare).
I'd like to meet the politician willing to take that leap...