I've lived in Canada my whole life. South-Eastern Ontario to be exact (near Toronto).
I lived in the Silicon Valley for 4 months last year, and am living in SV another 3 months this year (I'm actually in California right now). So I have a pretty good perspective on the American-Canadian divide. Of course my experience is limited to the state of California, and I'm aware that states differ immensely.
First things first. Canadian drivers are LEAGUES beyond American drivers in skill. Americans are very agressive and fast drivers, whereas Canadians take things a bit more chilled out. Of course you'll have your exceptions on both sides, but in the general case Canadians are more patient.
Canadians, in general are more intelligent. I'm not saying that all Americans are stupid, in fact there are plenty of incredibly intelligent ones (I wouldn't be here otherwise), it's just that the service sector is absolutely filled with total morons. For example: cashiers. In America even if the lineup is only a few people long I always have to wait at least 15 minutes, whereas in Canada small lines = short time. And then when you actually GET to the cashier they know what they're doing, are NOT ridiculously slow in pricing the items and actually know how to make change.
Continuing, the likelihood of you seeing someone arrested is pretty small, especially compared to the US where it's a daily occurence. In fact the entire feeling of safety is overwhelmingly more powerful in Canada. When I'm in the states, for some unexplained reason, I'm always afraid. Always. It's just this general atmosphere and pervasiveness of fear that emanates from everything and everyone. It's this general tenseness that seeps into your body and never leaves, until you do. This is actually one thing people don't really comment on because you ahve to be in teh US for an extended period of time before you really start to feel it.
Lastly, the food in Canada is a million times better than that in the US. The produce and meat products are worlds apart, and the dairy products actually taste good. The produce is probably the area with the biggest difference, I can't stand American produce. The funny thing is that a lot of Canadian produce comes from America! I think maybe California just has crappy distributors or something. Oh, and the food is clean in Canada, what i mean by this is your colon doesn't get backed up every week. It's probably one of the most annoying things about teh food in the states, it just stays in your system.
Diversity and racial tolerance are in another class entirely in Canada. It's still an issue to an extent, but compared to the US we're like a bunch of smurfs. Especially in teh bigger cities will you barely ever hear a racially motivated remark. I mean, people still feel that way and will comment to each other in private, but it's not flaunted and exposed for everyone around.
This is something that's probably unique to California, but the number of people with plastic surgery is far less in Canada. In fact the whole fake look is far less prevalent in Canada.
I guess the biggest thing is that everything is just so much more subdued in Canada. We're not as extreme in any way. Our nerds aren't as nerdy. Our luxury isn't as luxurious. Our women aren't as beautiful, but they're not as ugly. Our attitudes just aren't so extreme.