It's all about the gas fields and contracts that the EU wants to put in to control the gas from Russia. No one wants to talk about it, but that's part of the TPP Obama signed, to begin selling our American natural gas to the EU. The Ukraine president balked at new EU contracts, because Russia could give them a better direct deal. This sets up a new WWI resource crisis in the Euroland.
America won't go up in arms against Russia. Russia is too big of an ally. Probably leave it to the Europeans honestly. But I don't think the Russians should have just invaded the way they did. But eh. Bigger issues in our country to deal with.
I'll also note, that never in the history of the US, has Russia ever attacked the USA. The war mongering in congress by McCain and Lindsey Graham is a sham to the peaceful Russians. Obviously the corrupt/compromised US media is in on this, with their reports vilifying Russia over gays for the past 4 months.
Crimea and Ukraine are nuclear capable countries. Congress is just mad they didn't invade first. Secretary Kerry seems to think invasion is bad.. Yet he voted to invade Iraq.