We had an interview on the radio two days ago with someone from Hergé's (Tintin's creator) Succession who was involved with the movies. She said they were extremely pleased with the first movie by the way (though they had feared at first they had made a huge mistake of selling the rights to Americans after seing the first version of the script (faithful to the books - Spielberg is a big fan, but showing a great lack of understanding of the European setting and cultural details of the books and characters by both the Americans and New Zelanders. The Hergé foundation remedied that by immersing some of the key players of the production team in Belgian culture for a while and giving them Belgian advisors, and apparently it's all fixed up).

She gave two reasons why the movies were released two months earlier in Europe. The first is that in North America the big family movies like this are best kept for the Christmas season to maximize their BO potential. The second reason, the reason not to wait for Christmas for an European release too, is because of the huge difference of awareness and popularity of Tintin between North America (aside from Québec) - where Tintin is not well known to people not interested in European comic books - and Europe (especially but not only francophone Europe) where Tintin is a cultural icon known by nearly all. The studio and their partners are very confident the final movie is really good and will draw big audiences in Europe, and thought it better if the movie opened in America already a huge (they're hoping for "phenomenal" box office success in Europe, to go along the big North American marketing and mediatic campaign they have planned.