Why “except Quebec”?
Have you ever read the rules of a contest available on the Web or other medium that was available to “any resident of the USA or Canada (except Quebec)”? If you haven't… you haven't read many rules of North American contests. Almost all contest I've seen in English have that silly, but annoying, rule.
The reasons are few. Quebec has specific legislation regarding advertising contest, for example contests must be registered just like lottery or other gambling activities. According to Natalie Gauthier’s blog (fr), there is a registration fee if the total value of the prizes exceeds 100$ CAD. It gets more complicated if the total value is more than 2 000$ CAD. There are other requirements, including the necessity for the rules to be understandable, this means, with French being the official language of Quebec, rules must be available in French.
For more informations about the details of registration see Rules respecting publicity contests from the Régie des alcools, des courses et des jeux.