NATO should have dismantled after the war decades ago. They won. They agreed peace.
Instead NATO kept pushing up to Russian borders during peace times while Russia protested. They ignored Russia's concerns.
Well, what did they expect was going to happen? How could there ever be peace with Russia under these circumstances?
Tell me what would happen if a military alliance between Russia, Iran, China, North Korea etc etc started pushing closer to American soil, perhaps trying to get Cuba or Mexico to join?
We all know what America would do.
Long story, short: Ukraine should not be allowed to join for diplomatic reasons. It's a bit late now - Ukraine should never have been considered - but it would stop WW3.