I wouldn't say that's true when you think of it in a worldly context, America and Britain are a lot closer to each other than you might think. A group of Americans wouldn't have much trouble assimilating into Britain and vice versa due to things like shared language, etc. That goes for a lot of other Western European countries too, we might be different but in a worldly context we're pretty similar.
The UK had the US beat in pop music. Stuff like Genesis, Tears for Fears,Duran Duran, Madness, and the Jam still holds up, US pop music from era sounds really dated when you listen to it now.. The US had better R&B/Soul music, the only UK Soul artist I could think of is Hot Chocolate.