And Obama does want a gas war? You can argue that Russia would be hurt "more" by effective Russian energy sanctions than would the US or EU, but either way it's not a credible threat since there's zero chance Obama will carry it out. Mutually assured destruction may work as a deterrent but we're beyond that stage now. Obama and NATO aren't going to severely damage their own economies to that extent for the sake of some very small amount of geopolitical leverage on the Ukraine issue. I may disagree with some of Obama's policies but I give him credit for being a smart man and he's certainly not dumb enough to do something like that.
Why wouldn't Obama carry it out? The US gets very little of its oil and gas from Russia. The same reason why the US wouldn't be too concerned about sanctioning Russia's energy sector is the same reason why it wouldn't be that effective for the US to do though, we simply aren't their customers. That part is up to the EU.