Damn prankster, you're making so many good points that you *almost* have me changing my mind!
I'll attempt to counter some of them, but will perhaps fall short.
Ukraine won't be a part of NATO, ever. This war has set that in stone. As I recall, NATO didn't exactly invite Ukraine to be a member to start with. So I don't think that membership was dangled in front of Ukraine. There was talk of it, and if Putin reacts to that by invading, then ultimately the pretense wouldn't matter; he would have invaded regardless, imo.
Where do you stand on Finland and Sweden joining NATO? The Russians have tried taking Finland several times, so do you think this increases the chance of war breaking out between NATO and Russia (NATO being primarily us, of course...) Putin is evil, but not stupid, so he has to know invading Ukraine brought this on, or at least accelerated it.
I agree with your suggestion that president Obama's weakness when Putin invaded Crimea, emboldened Putin. But we deserve what we get when we elect feckless leaders, particularly as it related to foreign policy (so I'm agreeing with you that Biden has been wrong on every foreign policy position/decision he's ever taken.)
As little as I believe Biden to be capable (he is demented, after all...) when it comes to foreign policy, I think (hope?) that even he would not be so effing dumb as to get us involved in a shooting war with the Russians. He could gaffe us into one, because every time he goes off-script, it's like a pinball bouncing around a mine field. The one thing I believe with certainty is that Putin would never have invaded Ukraine on Trump's watch.
There is a silver lining to all of this, or perhaps it's just a pewter lining. But we are having our weapons systems tested in battle against one of our two main geopolitical rivals. And from what I can glean, even in the hands of Ukrainians those weapons are working pretty well. At some point that weaponry would have to be replaced, so at least now we know how to improve it for the next generation we develop. I know, that's not a lot to hang my hat on, but it's something.