Foreign policy
I think we tend to mix American foreign policy with the American people and unfairly assume all the Americans are arrogant and ignorant. I definitely don't agree with their foreign policy, but of all the Americans I have met in person have been in general, very civilized normal folks.
I wouldn't go as far as to say American and Canadian cultures are not too different though because they are different, and Canadians are proud of it just as much as the Americans are of theirs.