They are weary of Russia because Russia never got with the program. Russia does not believe that a peaceful future is possible, assumes the old status quo will continue, and act accordingly by continuing to invade their neighbors.
And just to preempt the inevitable whataboutism; America never got with the program either. Not really. But America isn't the one threatening Western Europe with war, and Eastern European countries like Poland and Ukraine choosing to align themselves with America/NATO to protect themselves against Russia speaks volumes about the relative threat of America vs Russia to peace in Europe.
Add to that how Europe absolutely botched both Bosnia and Kosovo and had full-scale wars there. Your arguments about world peace are bogus. Europe is encircled in a ring of fire made from ex-USSR, Middle East and Maghreb. All the wars in the world happen around Europe specifically. Maybe it's time to ask why.
As you can see now, not all of Ukraine wants to align itself with America/NATO.
Meanwhile, East Asia or Americas just don't see that amount of action. Africa does, but that's another story.
It's like someone is throwing wars towards Europe.
Last time Russia’s neighbors were invaded by them: well, obviously, now.
Russia also has a long history of being invaded from the West. That's why Russia is super nervious about NATO expansion.