Identity with a group is definitely an imported idea. The culture of early America had no room for groupthink or grouplife. Certainly, some of the early settlers may have arrived with the cultural bias toward doing things as an “organized” troop, but that notion got knocked out pretty quickly when the realities of dealing with problems one-on-one with nobody at your back became apparent, often with fierce and sudden onslaught. You either got really self-reliant, or you got dead, very quickly.
Only when the frontier was made secure, did the timid groupthink subspecies come creeping out and re-entering this country.
Now look. The groupthink is on the way to becoming a dominant characteristic of our society, and we are only saved from their further depredations on our liberties because they have sometimes mutually antagonistic cultural positions. Thus they end up fighting each other.