The US paid for its alliances, hegemony, and safe shipping lanes by providing a comprehensive nuclear and conventional security umbrella via NATO.

Framing calculated realpolitik as an act of charity that the people of Europe should be grateful for is pretty cynical. It's always been a trade-off. The president has always complained publicly about the cost, precisely because admitting that reality doesn't win votes at home, but narratives about European leeches taking advantage of the US does.

If you want to see what it will look like after the US stops paying the bill for its incredibly privileged position, you can read about how much fun the process was for Britain in the 1950s.