German ancestry is #1, English ancestry is #2

[Filuwaúrdjan]

My theory is that one is far more likely for people to tag their English ancestry if it was via New England as opposed to the South.

Stated 'English' ancestry in the US census has for a long time mostly indicated known ancestry from New England, which is why the patterns are interesting even if they don't show what they purport to.

[Filuwaúrdjan]

Anyway, nearly every White American* has at least some English ancestry: the exceptions would be from certain groups that retained the status of ethnic groups for longer and have not assimilated in full or were very late to do so. Substantial proportions in the Appalachians and wherever there was significant Appalachian diaspora later will also have Welsh ancestry: now there's your ultimate forgotten ancestral grouping, later migration to Scranton, PA and some Mormons notwithstanding.

_{*And, if we're being honest, most Black Americans, though rather more distantly. It is the way it is.}