Since when? I don't mean the defiant "Since when?" meaning "Sez who?" just "When did this actually happen?" I'm pretty sure that in 1940 plenty of Americans still thought of England as their mother country.
Even now, I don't see anything from French or German or Spanish or Chinese TV having the appeal over here of Downton Abbey and other British television series over here even among people without a drop of English blood. I don't see many people linking to articles in other foreign papers, either.
I do have to admit, though, the general decline of British TV and the fact that they aren't fighting Hitler now tends to make our affinity with Britain weaker than it once was.
The UK isn’t what it was in 1940, what with the huge mostly muslim immigration. I have a friend from London (late 30’s) and she says when she goes back home to visit it isn’t the same country she grew up in.