Speaking of Celtic nationalism, I remember reading book two decades ago called "American Mania". One of the premises of the author - Peter Whybrow - was that the Celtic/Germanic conflict reappeared millennia later in the American Civil War. Strangely, the Confederacy was overwhelming Celtic of origin, while the Union Army was primarily Saxon/Germanic. Strangely, the sides faced themselves off on completely different issues, but the deep seated ethnic divide was there in the background. Also, to this day Americans of Celtic backgrounds are much more likely to be in favor of Donald Trump, than traditional Anglo Saxons. There may be an epigenetic element to this.