Takarashi
^ What the above posters said. Some of the other trailers offered some insight into Connor's motives, primarily that he's not interested in being involved with the war for supporting either side, only that he wishes to find and kill the Templar that are a part of it all. From what I gather, though, he leans more toward the Americans in support for whatever reason.
Well, Connor and George Washington become good friends later on. Maybe thats enough reason to fight with the Americans? Also remember what the Americans were fighting for in the Revolutionary war? Freedom, and the Assassins fight for freedom as well, quote Ezio Auditore "I will help you as long as our interests are aligned."