You make a good point that Canada is being used mostly as a staging area (boy, THAT makes me feel better), but that there is no real evidence that Canada is being threatened. Other nations have also been so used by terrorists. The 9/11 guys hailed from Germany, as I recall.

As for why Canada hasn't been targeted--so far. At the risk of being repetitive, Canada is not a major influence in the world in either the economic, military, or the cultural sense. In other words, it isn't really any more of a threat than Iceland is to the Islamists.

The United States, for good or ill, has been a large influence in what goes on in the Middle East. It has supported Israel, the single bastion of democracy in the whole area. It repelled Saddam Hussein when Iraq attempted to conquer Kuwait, and whatever other nations would have been next. Control of most of the Mideast oil supply by the Baathists was a real possibility before Gulf War 1. The resolution of Gulf War 1, with Saddam continuously straining at his U.N. agreement restraints, required stationing forces in Saudi Arabia and elsewhere, which was one of the main reasons Al Qaeda got rolling in the first place.

Although, to be fair, Canada has given support in the overall war against terror (including combat troops in some cases), like many other nations, Canada is largely comfortably placed in the hammock of the worldwide security that the United States has been providing for decades. America has received largely contempt for this, but what else is new.

Isolationism is easy when someone else is taking up the slack.