The US are the ones who said "fuck the EU", that Putin was like Hitler, and blamed Russia without evidence for the plane crash. That's being arrogant. The US have been implied in many wars in the past few years, but who's belligerent again ?
Just like other countries where the US went in the past (and gave false reasons) their aim is ressources. John Kerry has started fracking in Ukraine (despite the sanctions) and everybody knows about the pipelines that feeds Europe in gas. The US want to control those pipelines. They've realized their gas from fracking is worth nothing so they want to start a conflict with Russia and Europe so they stop feeding gas to Europe and so the US can sell theirs.
When the Malaisian plane was shot, Obama immediately accused the Russians. Obama wants war, admit it or not. If you know about WW1 you know this is the kind of event that could have started it again.
It's the Russians right to move troops in their own country. But when European and US aircrafts have been sent to Nato's bases in Poland and around Ukraine early in the conflit, it was against international laws.
If Putin wanted war we would have war. My opinion is Obama wants Putin to close the gas pipelines in Ukraine and stop selling his gas to Europe so gas prices would go up and the US could sell their gas to Europe (along with singning trading treaties that favor them). Putin knows if there's a war it will cost a ton of money from both Russia and Europe, while the US would watch. He may be an evil guy, at least he knows if he waits and let things vent it can only help him and not the US.