Let me start by saying that I do not know of any specfic bad rap Canada gets in any roleplaying games. However, I can see WHY they would get a bad rap in most modern era games.
#1) Nowhere in the world is gaming as prevalent as the US. Take out console and computer games, I'm talking people who buy dead tree books to play with minis, dice, figs, cards, or other in person social interaction games.
#2) Because most gamers are in the US, many games are written by US authors, and the 'default' setting is usually somewhere in the US. It's nature that we write what we know, and using your home country as a premise makes writing easier.
#3) Extrapolate 1 and 2, and suddenly to create a game other than "Real Life Gaming" you need to have the hook or the twist. Zombies, apocalypse, etc. Sure, that could be enough for some people, but gamers like fluff, and we want to know what our close proximity neighbors are doing. Also, maybe the game needs more adverseries than just the hook, so we take the 2 closest countries to us and make them "eeeeevil" (TM).
Now, adding those up, you get a communist canada, which is either:
a) Misinterpretation by us southerners as to how your government is handled.
b) Extrapolation - seeing what happens if we take your current government to the extremes
c) Pure fiction for the purpose of gaming fun.
Dude, relax. You're in CANADA, eh?
Hell, if you want to kill this big stereotype, then write your own setting where Canada, eh, is the greates country in the world and the US is the axis of "eeeeevil" (TM).