U.K. bloke here…I don’t use it personally, just because, but yeah we say it for anyone from the USA.
When I was about 10 or so someone local to me had a lawsuit because his colleagues called him Yankee and he claimed it was racism, fairly certain he won, but it was an obscure case.
I appreciate I’m nitpicking, but we all use rhyming slang. Probably changed over time.