I can have an Aussie call me a Yank and i think nothing of it....because we don't have the same history with them as we do with the British... check what AZI quoted with the
"The British liked Yankee, too, when they wanted a derisive epithet for the New England provincials. They set it to music in the song "Yankee Doodle," said to have been composed by a British army surgeon "in derision of the provincial troops."

THAT'S where it came from..not a term of endearment..but a slam to their former colonists.

But for whatever reason, seems a lot of Brits think they can make jokes that Americans are stupid, uncivilized, crude, whatever... and expect not to get an answer back because it was a "joke"...well, it gets pretty annoying very quickly.

Grant me the senility to forget the people I never liked,the good fortune to run into the ones I do,and the eyesight to tell the difference.