Simple solution to both add variety and fill the required "insert controversy here" event as well as make the campaign substantial, just make a world war two Call of Duty that attempts to tastefully and explicitly reference and pay respect to those that were killed in the holocaust, offering a legitimately realistic and emotional experience. Of course Something with this much baggage and no room for error will probably drive off the high school hardcore gamer demographic and I doubt any of the past CoD devs have the finesse and taste to pull it off. So you don't exactly have to get rid of Americans, just stop shoving the "America is Super awesome Fuck Yeah!" Attitude in an international markets face.