Okay so you can't respond to my question.

I did.

No one except the very stupid walks up to someone who likes to fight, is always fighting, arms themselves to the teeth as a national priority, and doesn't get mainstream objection from their citizens about 'droneing' people. You don't want to get involved in that war. There isn't anybody who is capable of stepping up to stop it.

Europe can't be touched because NATO Article 5 says, "An attack on one is an attack on all." That means we consider it the same as an attack on US soil. We do NOT take kindly to someone attacking our soil.

If you want to see how peaceful Europe is as a result of that security guarantee, the Swiss Air Force had part time hours. They closed after business hours and handed over coverage to the French air force if I remember correctly. It is the type of arrangement you get when no one has any worries at all.

The US benefits from NATO in the form of customers via the 2% guarantee that they agreed to. NATO benefits from having the US as a reliable and unreasonably overpowered military ally. Its a very tidy arrangement where everyone wins aside from the US taxpayer who has been keeping up our end while NATO members slip on the 2% that they agreed to.

tl;dr They agreed to the 2% to be part of NATO. They don't have to be a part of NATO, but they know how valuable it is. Look at Ukraine, we would never have let that happen to Poland. it would have meant war.