Yeah that should be fine. What I did in the past with US versions was download a copy then just buy the CD Key from a store in Canada.
Sorry I can't help you though, quit US WoW after TBC came out.
Also, do not worry too much about getting WotLK NOW, unless you plan to use some of the features it has access to early on like say Inscriptions, or DK's or the like. It will take you quite a while (depending on how much you play), to get to WotLK only content.
