NATO can't just abandon nuclear treaties. And trust that, as it controls 90% of the pipeline of oil between Russia and Europe and that because the conflict arose during highly contented offers for Ukraine to join the EU, that NATO is doing everything it can.
There is a geo-political game going on in Ukraine right now. If you think you are getting an accurate assessment of the situation on CNN, MSNBC, and Fox News, you'd be about as right as you where on Libya, Iraq, and the other dozen or so major conflicts that ended up being nothing but full of lies.
It's in US's best interest to see Ukraine fall into a state of constant chaos. It's in Russia best interest to see Ukraine stabilize. From those two points you pretty much can infer who the aggressor is going to be.