I'm not anti-American, but my dad is... kind of.
My mother is originally from the States, so when she wanted to move back, they struck up a compromise and moved to Canada. We always joke around that my dad isn't proud to now be a Canadian, he's just proud that he isn't American!
I guess it's a lot of things they hate about Americans. It's generalizing, obviously. I don't hate Americans as individuals, it's just a lot of things go on that wouldn't happen in Canada. They're flashier, even. Canada and Europe get paint colours for cars that don't sell in the States at all. I'm not sure how to put it. Arrogance? Ignorance? Again, not all Americans, obviously. But you've got the reputation, guys! Prove us wrong!