yes, the U.S and Britain were allies, but who specifically overthrew Hitler would have been the U.S and the USSR (Russia) for when Germany was defeated the two had been invading from opposite ends (north/south or something) at met in the middle. So US, Britain, and the USSR. I'm pretty sure that's all because the "big three" or leaders of the allies were Churchill (Britain), Stalin (Russia), and F.D.R (US).