In some ways I would like the US to be playable but if you make the US playable then you would have to make every other minor nation playable. Besides historically the US couldn't even think of invading Europe. First its navy was crap at the time and European nations had larger armies then the US had people. So historiacally it wouldn't make much sence seeing as there are only 10 playable factions. Besides the US get there own campaing anyways.