Estimated Breakdown of "American" Ancestry in the US?

[Adam Griffin]

In basically any non-urban, plurality-"American" area within 75 miles of Appalachia where these people can trace their lineage back to the area more than 2-3 generations, you can substitute "American" for "Scotch-Irish" (save for a few notable examples, such as the German communities in Eastern & Middle TN etc) as a plurality group of these "Americans" at minimum.

As far as why this phenomenon has emerged, I think the gist of it is pretty simple: the East was settled first - meaning it's the oldest - and so descendants of immigrants are far more removed from their ancestral roots than communities further west. As to why it's mostly a Southern phenomenon rather than something up and down the entire coast, the North obviously continued to attract wave after wave of white ethnic immigrant groups that arguably kept distinct identities in place far longer than would have otherwise happened if it had been the South attracting these European migrant waves (and was considerably more urbanized, allowing large groups of distinct migrant groups to huddle together and maintain their identities).

In many respects, the South is the "oldest"/furthest-removed from its European roots than anywhere else in the nation.