Canada dodged a bullet on 9/11. If the US had uncovered any connection between the 9/11 terrorists and Canada - even a minor one - they would have slammed Canada and slammed us hard.
Even though not a single piece of evidence was found linking Canada to 9/11, many Americans believed for years afterwards that Canada was a major security threat to the US. Even though the US let the terrorists into the country, taught them how to fly airplanes, and missed warnings that they were trouble, it was Canadian immigration and domestic security policies that were under fire.
The American populace suffered a mass derangement after 9/11 that lasted for four years. In their derangement, they thought that invading a completely unrelated country and killing hundreds of thousands of people was a justified response. Hardly anyone in the whole world believed the lies justifying the war - with the exception of the vast majority of Americans. Even Britons didn't believe it.
Over the last year or so American media has finally started to question the war, but now it's too late. The frightening thing is that the Americans could do it again. It might not be a military invasion. There are other ways to attack a nation.
We even know where they're going to do it next time: China.