From the article: "Why would you want to do this? For countries that drive on the other side of the road. Like Canada. But, oops: they drive on the same side o

From the article: "Why would you want to do this? For countries that drive on the other side of the road. Like Canada. But, oops: they drive on the same side of the road, not the other side, so we see humorous bit #1: feigned American ignorance of Canada. But oops, again: assuming a left-side steering wheel is an AmericanCulturalAssumption - you might really want to change the side it's on if you're British and you're driving to Canada. That's humorous bit #2: we've caught the picky people in an unwarranted assumption (and a USAian one, at that!). Humorous bit #3 is the sheer unlikelihood of a British (or Japanese/Australian/Indian) person driving to Canada, after all. That's the explanation. But it doesn't make the joke any funnier."