Hunh... I'd always thought the "damned Yankee" thing was a relic of the Late Unpleasantness.
Joseph Plumb Martin, c. 1778 (or still 77? Rather lost track..)
"... The regiment that I belonged to, was made up of about one half New-Englanders and the remainder were chiefly Pennsylvanians*, - two setts of people as opposite in manners and customs as light and darkness, consequently there was not much cordiality subisting between us, for, to tell the sober truth, I had in those days, as lief to have been incorporated with a tribe of western Indians, as with any of the southern troops; especially of those which consisted mostly (as the Pennsylvanians did,) of foreigners. But I was among them and in the same regiment too, and under their officers, (but the officers, in general, were gentlemen,) and had to do duty with them to make a bad matter worse, I was often, when on duty, the only Yankee that happened to be on the same tour for several days together. "The bloody Yankee," or "the d—d Yankee," was the mildest epithet that they would bestow upon me at such times...."
(lest you take the speaker as some shrinking violet, the events described in the previous year or two of service...um... let's just say the images swimming in that man's skull I'm quite happy aren't in mine. *shiver*)
* Backcountry Pennsylvania at this point is mostly German and Scots-Irish. Pennsylvania was the most welcoming place for those of their respective dissenting faiths at this point, and upon arrival were quickly shooed into the backcountry by the Quakers as a barrier against the natives, back away from decent folk. From there both peoples pretty much leapfrogged each other all the way down the Appalachians.
... is also where we get the Kentucky (née Pennsylvania) longrifle.
German tinkering meets Scotch-Irish cussedness.
Well where did you think the American rifle culture came from? :)