I agree with a lot of that. The question has to be asked: why are 300 million Americans paying to support 600 million NATO ally members from 150 million Russians? It was one thing immediately after WW2, but now the Europeans can certainly afford to shoulder more of the burden of their own defense. Germany is spending only 1.19% of their GDP on defense...
Peace and security, the the result of that has been unparalleled peace and prosperity not only Europe but us as well. While most European NATO countries don't contribute enough our contribution has also dropped significantly as well, from 6 US Army divisions and supporting troops of roughly 213,000 soldiers to just 3 combat brigades of about 27,000 now. And that is just the Army. Ours is one of several commitments while for almost all the Europeans it is their only one.
Also from a realist point of view our troops stationed in areas around the world give us an outsized say in what goes on in those countries and regions, much more so than if we weren't there. I would rather us have that say and use it to our interest than leave to others.