If any Canadian province leaves (We were all thinking Québec, weren't we?) Canada won't survive well. I wonder if it can be argued that Canada's health care system is essentially paid for by Alberta oil.
Now, with regard to the first sentence: Neither Bush nor the US in general is particularly eager to get Alberta's oil. Yes, it'd be nice to have it within US borders for national security purposes, but Canada needs to sell it more than we need to buy it and it won't be free -- US consumers still have to buy it no matter what. It just won't be subject to whatever tariffs or other taxes Canada puts on it.