The most famous Canadian expression is "eh" (the french equivalent that's used the same way is "bein") well there IS a reason we say it. It's a politeness marker all languages have them ours is just well known. Eh is not exclusively Canadian although I think we say it most. We say it becuase we are trying to include people in conversation and keep them from feeling alienated among other reasons. The closest American usage to eh is "huh" when inserted into a question like eh,  is intended to bring you into an assertion by making you part of it. Pretty mind bending eh? It should be noted "eh" is more versitile then "huh" and has more meannings. On occasion "eh" is snorted instead of pronounced "eH emphasis on the h sound" if its snorted at you its derogatory but its uncommon to be used this way. I don't know if "heh" is derogatory in American like a snorted eh but it sounds like a snorted eh so it feels like sarcastic disinterest and  disgust to my ears. When I hear it I suspect someone's being rude at me and my feelings are hurt and I usually involuntarily pause out of surprise. I strongly suspect a snorted eh and heh are the same and I'd appreciate an email if someone knows better. 

There's about a gazillion different meanings between American and Canadian English but it gets even more complicated ...Canadian English has several sub dialects as does American English. Now then I was going to include my own American Canadian dictionary but you know what that's been done over and over and over now so what I will do is point you to sites about it. Do look into it I think you will be quite surprised and the more you dig the more different you'll see we are. If you enjoy this don't stop at these keep looking the more you look the more conversations that didn't go well or are confusing make sense.