Canadians have always had an anti-American mindset. I live near the Ontario border and this is nothing new. But I have to laugh when they show they are just as human and not above that.
As you can tell from my locale and tagline, I'm not too far from the Mexican border. That nation is populated by people who hate America -- but they swarm across the border to take advantage of our largess, all the while waving their Mexican flags and speaking their Spanish. They don't adapt to our culture or our values.
The anti-American mindset of Canadians is a harder puzzle to crack. We speak the same language, are mostly descended from the same culture and much more than the Mexicans, share the same values. Yet, like you, I've detected a smugness on the part of many Canadians when I travel there. Sure, we'll have regional (and national differences), but Canada ought to be thankful to have a truly good neighbor like the United States.