Well, it turns out that W.i.t.c.h.'s immense popularity in Europe has prompted Disney to give it a go in the U.S. They're not about to start publishing comic books in the U.S., but it looks like W.i.t.c.h. will be sold in novel form, with "comic inserts".
http://www.clubwitch.com is the homepage URL for the U.S. market. It has a story overview and character bios, and other stuff. Each character bio has something in it, like some pages from the comic, a trailer (I guess it'll be a TV ad, or maybe shown before Disney movies), etc.
The series obviously was aimed at girls (some of the really girly cut-out stuff inside this special issue we got proves that), though it seems to have developed quite a following among both sexes overseas.
Will it catch on over here, considering that it's in novel form instead of comic book form like it was intended? I guess they're doing that because the U.S. executives are thinking, "Gosh, it'll be Harry Potter for girls!" It isn't published in novel form anywhere else, as far as I know (the Italians are complaining about these not being made available in Italy, from what I could see when skimming through forum posts about the series being introduced to the U.S. market).