Passing Thought : Why militarization?

My question is straightforward, why Risc a nuclear war for Ukraine? Why is America so eagerly wanting to protect a country largely split in two with huge problems with corruption and organized crime and above all, a country that isn't a NATO member? Why this offensive against a formerly "friend", Russia? American propaganda is running wild in Eastern European countries, it seems the US wants to create public support for such beligerant attitudes. Let's hope humanity will prevail and this demonic plan will fail.