I dunno, guys. I don't claim any particular insight into US motives, but I just can't convince myself that oil is it. Someone posted earlier about Iraq being the world's second largest oil reserve. I think he needs to rethink that.
If the US really wanted control of vast oil, I truly believe they would look to the north. Now, don't start sputtering about global outrage and how the world wouldn't stand for it. We are the only ones who would be really upset. The rest of the world already thinks we're the same country.
Alberta's oil sands are the richest reserve on the planet. There's that sputtering again!! No, it's not too expensive to extract. Extraction is far cheaper than war. Unless I'm mistaken, the expense argument went out the door when oil blew through 50 bucks a barrel.
What follows is opinion. If the US really wanted oil, they could likely get all of ours, without firing a shot. A few well-places trillions of US dollars, strategically applied, would secure pretty much whatever the You-alls want from Canada, for as long as they want it. I'm not sure they have anybody bright enough to pull it off politically, but I'm confident they could do it financially.
End of rant.