More to the point, other countries would have to start spending money on their militaries. Most NATO countries don’t even meet the purported spending goals, and that’s just for the single goal of deterring Russia. Many countries benefit a lot from America’s military spending, both by being able to utilize the peace and by being able to save their own money.

Whether or not this is a good or fair state of affairs is a different question, but there are a lot of reasons why things are this way.