I am inclined to agree that’s so except that some of the more devout among the English and the Dutch remained as “Yankees”. Scots-Irish headed for the frontiers and just kept expanding until their leading edge ended up in east Texas. They were more devout in a way, but less so in a way.
This is an interesting topic and might be worthy of a thread all its own, but the “stay behind” Yankees adopted a more social type of religion and morality, which is why all the major protestant reform movements in the U.S. originated there. The idea was to reform society as a whole. “Yankeedom” extends into the Great Lakes region.
Scots-Irish were more oriented to personal morality and didn’t have much in the way of societal cohesiveness beyond the extended family.
It’s interesting that today, and despite secularization, the “reform society” segment of the U.S. is still principally on the eastern seaboard (and it’s echo on the west coast) while “reform individuals” is prevalent in a swath from southern Pennsylvania into the Appalachians, upper south, Smokies, Ozarks, Ouachitas and Texas Hill Country.
And political party allegiance tends to follow the very same pattern and for the same reasons.
Other parts of the country have patterns peculiar to themselves.