The thing about Canadians (and I say this with authority is that I am one...) is that they have a huuuuugggge inferiority complex when it comes to the US. It is a bitter sibling rivalry that is fueled by the highly successful, over-confident brother to the south that gets all the attention. Of course Canadians will act out in a negative way, just as the younger neglected sibling would.
It doesn't help that to Canadians, it seems that Americans themselves barely even notice their existence. Everyone has stories of Americans who come to Canada expecting to see dog sleds and igloos. I had relatives from Kansas go to visit the rellys in Toronto and decided "while they were in the neighbourhood" they would go and visit the family for dinner in Edmonton. Three and a half days later... they arrived totally shocked that Canada was so big. It's stories like these that fuel the sibling rivalry - all the big showy stuff is won by Americans but it's those little things that make Canadians feel like they're gaining, in even the smallest of ways. Canadians in the past have had a good reputation as tourists abroad and because Americans generally don't, they try to distance themselves at all costs. Kind of like being at camp with your brother and completely disassociating from him as soon as the parents have left.. And it is for these reasons that Canadians hate being called American.
Having said all of that, I think it's time Canada grew up, put on their big kid pants and get on with it standing on their own two feet. Beating down americans, and even worse constantly acquiescing to them in things such as trade agreements etc.. is old and tired and quite frankly, not exactly the most appealing part of Canadian culture.