There is plenty of blame to go around. But you are going to get what you want: A completely militarized Europe who does not have to answer to us when we pull out of NATO (as that is coming from these dipshits). It is going to be awesome. Odds are your kids will look good in fatigues!
I think Obama, Trump and Biden (in that order) deserve the most blame for Russia’s invasion of Ukraine. Romney and McCain understood Putin’s ambitions to restore the Russian Empire and allow Moscow to project its power into Europe. Biden was slow to act, but at least he moved away from Obama's faulty view of Russia.
Unfortunately, we now have a surrender monkey in charge. Trump and the MAGAs want to take us back to the 30s, a period of rising fascism, strongman rule, trade wars and tariffs, and of course appeasement.