If you spend some time in the USA, even on holidays, I think you notice the differences much more (unless you want to believe there aren't any). For one thing, Canadians are generally more reserved, particularly between people who don't know each other well. Americans seem to be more immediately friendly and talkative, and will get in your face and blab away about themselves, or whatever. It's fun and refreshing, but it can sometimes feel uncomfortable if you're used to living in Canada. How we talk and act between strangers seems to be somewhere between the UK and the USA. Much warmer than the UK, but not nearly as intimate as the States. Of course, there are differences between regions in Canada and between regions in the USA - but certainly as a guy who has lived in (mostly) Alberta and (only for a bit) BC, I've noticed it a lot.
edit: I'm talking about between... say a cashier and a customer at a store, for example.
That only makes sense, though. The US is big, flashy, noisy - when they put on a show, it's way over the top. They like to be number one and they eagerly show it. Canadians, on the other hand, are more humble, perhaps because we know how it feels to be next to a country which is, unabashedly, flamboyantly, number one. (I should note that by "number one", I am talking in terms of influence, power, and $$)
But we don't get lost in ourselves nearly as much. We have a more international perspective - nowhere is this more evident than in our news programs, which are very different from American ones. We are more tolerant of difference of opinion and culture, not wanting to offend anyone or step on anyone's toes. It's hilarious sometimes. I think we are obviously more "left-wing" when it comes to issues like health care, education, social programs, foreign policy, etc. It's debatable whether our system works better (eg. taxes), but I think it reflects a genuine value - we feel we have a responsibility to directly help out the little guy.
I could go on and on but this post is going to get ridiculously long. I love our country, flaws and all. It's a good work in progress. You've got to love it: getting the Tim Hortons coffee in the morning, complaining about the weather, playing and watching hockey, skiing and hiking in the beautiful rockies, sailing on the coast, Montreal, Quebec City, poutine, the search for national identity, and on and on and on and on. We're so lucky we don't even know it.
Remember that contest to find a Canadian version of "As American as apple pie?" The winner was "As Canadian... as possible, under the circumstances." Brilliant!
edit: took out a paragraph of rambling