Canadian here.
I think that the word is just simply more polite, or even "docile"? We are mostly hard working folks that care for our families, and yes I would agree we are somewhat reserved, compared to say the southern U.S.
Having said that, you'll most certainly find pockets where they are just as loud and aggressive as any American, guaranteed.
I do agree that when Yanks visit us they can't believe how different it is up here. The first thing most people say is "Oh my, it's so nice!"
Yep, you're aggressive, the last remaining superpower in the world, and we're.....nice.