We aren't ruled by England and never have been. As mentioned previously, Scotland won the war of independence against England - a long long time before the US was even conceived.
There are so many things that you clearly don't understand about this situation, feel free to shut up about all of it until you do.
Somehow it's funny that Elizabeth's greatest conquest for England still is not accepted in full. Scotland was won by simply having no heir and having the Scottish king reside in London, making him an English one essentially. By the way, why should the nationality of royality matter all that much? - the rulers of England were of French(Plantagenet), Welsh(Tudor), Scottish(effectively French again), Dutch(Orange) and afterwards German noble houses..
England was the dominant part of Great Britain at all times, as was Russia for all states it was part of (making it viable to have the Georgian Stalin as a Russian leader), as was Prussia for Germany later (Frederick in Civ4).
So far, every civ game had America, Aztecs, England(!), France, Germany, Russia, Rome, Greece, Egypt, Persia, India, China and Japan in its vanilla version, if I'm not mistaken, always under this names, other civs to follow in expansions. (and except for the HRE, I could live with all of them)