As a Canadian who's spent a LOT of time in the US thanks to work (thanks, @jlw!) the major difference I've noticed is that because politically the issues we have with our government usually aren't critical issues like healthcare, security, or foreign policy, there's a lot less ire towards the government in general ("Government is trying to take my hard earned money"-type conversations are less prevalent here, which I always thought to be ironic because the Government here really is taking more of our money, but hey)
Our news isn't a bunch of talking heads arguing how the government in power shouldn't be there or has no competency, and our reasonably strict lobbying and campaigning laws prevent our advertising being clogged up with political ads (political groups can't even get non-profit status here! That unfortunately includes the EFF, sadly).
I'm a predominantly Aboriginal Torontonian, living in a city that is majority immigrant, and yet I almost never think about the sorts of issues I hear about regularly in the US regarding racial or cultural tension. It's not that those issues don't exist here, but that they tend to be universally condemned by the media and government and treated with the appropriate ire by the community (another thing most Americans don't know about Canada is we don't have the freedom of speech laws the US does - it's much easier to have something classified as hate or criminal speech here).
It's a little weird, to be honest. Every time I visit the US my usual reaction is "why is everyone so angry all the time?" - it seems like every TV station, billboard, or idle conversation I hear is simmering with a sort of resentment and defensiveness that just doesn't seem to exist up here in the same way. My guess is, more than anything, that that's how we get classified as "nice", more than anything else. I don't feel like I need to defend my way of life from my own country, whereas that seems to be the narrative of a lot of what I read about the US lately.
That area of the country is both beautiful and incredibly welcoming. I got to spend several days in Nova Scotia and New Brunswick last fall and one of my thoughts was "this whole region should be the Canadian ambassadors for the world". great people out that way.