Up until recently, Health Canada barred the use of caffeine in non-cola soda products. Apparently the laws have changed now, though.
Mountain Dew isn't associated with caffeine up here. In fact, Canadians are (or were, prior to the change) just as likely to be shocked that American Mountain Dew is so full of the stuff -- we're not used to seeing caffeine in pops other than Coke, Pepsi, and similar drinks.