How did there come to be countries with right-hand drive and others with left-hand drive?
I suggest you read the article at wikipedia here http://en.wikipedia.org/wiki/Left_hand_drive#History for a complete answer. In short, America moved to the right because of it was easier to drive large frieght wagons in the 1700s. France and much of Europe changed due to political reasons as detailed in the article. Canada changed to make it easier for border crossing the States. Sources: http://en.wikipedia.