That's a wonderful account you posted.
When my dad was in WW II. Being in the C.B.I. ( China-Burma-India) campaign of the war, he came into contact with a lot of British soldiers. Of the first time a British soldier called him a "Yank ", dad told me he wanted to knock his block off. And I have heard about other Southern fellows having the same reaction when they were called Yanks. Before he went into the Army, he had not been out of Arkansas, except for a trip to Oklahoma, so when he had to deal with " Yankee boys " (that's what he called them ), it was a shock. But you know what, he made friends with some of those Yankee boys and he stayed in contact with a couple of them until he died in 2007. I guess when you are in the jungles of Burma fighting for your life against the Japs, it really didn't matter to him what state the guy next to you is from.