Checking originality of concept

Hey guys, I'm starting up a piece of fiction here, but before I get deep into it I need to make sure I'm not ripping off someone I've never heard of.  So has there ever been a novel based around the essential concept that the American Revolution failed, and that England controls the USA even today?

I don't think anyone would be interested in buying it. Unless it's a life ambition or something I wouldn't bother.