When you ask me to look at the horror of the world wars, does that include the horror of the only country to ever use atomic weapons in conflict deliberately dropping them on cities they knew were full of civilians? If that's what the American version of "peace" looks like, I'm not interested in the American version of "peace". The Soviet Union never deliberately nuked New York. China never deliberately nuked Taipei. North Korea never deliberately nuked Seoul. Iran never deliberately nuked Jerusalem.
You propose a hypothetical future where you guess that a world without US "stability" involves nuclear weapons, while ignoring the fact that the world with US "stability" already involved them. History speaks louder than hypothesis.
Please tell me what the last 80 years would have looked like with an isolationist US, weak or no NATO, and an unimpeded ascent of dictatorial regimes. Answer: even more of all those things you purport to hate.
The US is the worst superpower, except for all the other ones. The choice is not between good and evil, it's between evil and less evil. (Just like presidential elections.) Don't be naive and empower the greater evil just because you're displeased with the lesser.
I'm not saying you should stop pressuring the US to act morally, but asking it to leave a power vacuum is dangerous.
Edit: typo
Modern anti-vaccine nuts have spent so long living without measles that they've forgotten the good that vaccines do and take their good health for granted. Anti-US-power nuts have lived in a world largely without large-scale conflicts, held in place by our NATO allies and the credible threat of force, and you've forgotten what a world without that stabilizing effect looks like. Spoiler: it looks like the 30 year war but with nukes.