First of all the Keystone Pipeline would take almost two years to build, which hardly solves the problem. Secondly, it is natural gas, not oil, that's the main problem. Thirdly, as you say above, Russia's response could even become worse than what already has happened.
Whatever is decided, and I do think something must be done, both the Europeans and us should be on the same page, but I don't see the Europeans much going beyond complaining. I listened to the former U.S. ambassador to the Ukraine last night, and he says there's not a whole lot we can do without the Europeans being aboard.
Right now we need to see what Putin will do next, particularly in terms of the rest of the Ukraine. If they take over a larger section, all bets above are off the table, and I think you may well see the Europeans coming on much stronger and backing it up with some real sanctions.
BTW, isn't it just pathetic that so many of the Republicans are trying to make political hay out of this at a time when we're involved in a crisis. To me, such debate belongs in Congress in regards to which actions should or should not be taken instead of using this for their 2014 campaign.