There’s a lot you go over. But I disagree in degree, not in principle. There’s nothing you said I would dismiss out of hand. Yes, America wouldn’t put up with Russia arming Mexico or Canada. I don’t believe the biolabs are important. There is a general neonazi problem the world over, in Ukraine, in Russia, Europe, here. I only see it as a pretext. Putin should have realized within a few days that his assessment is wrong. Maybe he did but has trouble backing out. Who knows? We didn’t leave Afghanistan even though we knew it wouldn’t work out early on.
My billion dollar question is why Ukraine didn’t accept Russia’s demand for neutrality. Like you say, it seems reasonable. NATO’s whole existence is based on distrust of Russia. It doesn’t need Ukraine stay safe. If it did, it would be at war with Russia now. So, Russia worries more about Ukraine than Europe. There should be more respect there.
When I was young I never learned about Turkey, about why Russia tried to put missiles in Cuba. It’s the same now. Americans don’t understand what lead up to this situation. Like you say, if they thought about it for 2 minutes they’d see so much doesn’t add up.