It's quite an interesting monicker. Outside the U.S. it means any American, while if you are from the American South, Yank or Yankee means any American not from the South. Regardless of whether your respective state fought in the Civil War or not. I remember being called a Yankee on a cruise by a British guy and I said "hell naw, I'm not from the North" and they were totally confused. To Southerners, a Yankee is someone from Seattle as well as Boston. This is a term someone form outside the South always confronts; I remember going on a date with a girl from Boston and jokingly calling her a Yankee and she responded "Oh no! I'm a Redsox fan!" lol. But I would say in the 21st century it normally is a moniker of jest, although I believe the cultural difference is still prevalent.
That being said, to a Southerner the term Yankee also comes with stereotypes: loud, talkative, greedy, secular, urban etc.
Of course, like any stereotype, including Southerners as stupid, redneck or backwards, they are not true. But as a graduate student studying Southern history, we talk about the perceived difference between the American North and South ubiquitously
Seeing you're from the Republic of Ireland, the interesting aspect about the history of the American South is it's similarity with the rest of the world. Unlike the rest of America, the American South has experienced defeat, occupation, long term poverty and struggles with industrialization. Which makes in interesting enough, for me personally, to study it as a career!
