I think the war between the English and Scots-Irish idea is stretching things. English descended people made up the considerable majority in both sections.
Scots-Irish were concentrated in the mountainous areas of the South, and thus a surprisingly large number were Unionists.
The New England states at the time were heavily English, but the Mid-Atlantic and Midwest states were very mixed. Large percentages of people in midwest states came from the South.
Davis and Lincoln were born within 9 months and 100 miles of each other in the KY mountains. Davis went south and west, and Lincoln north and west.
Years ago someone sent me a match of historical migrations from Europe to America, and my recollection is that it did indeed show a much greater migration from the "Seeds of Albion" (Scotch-Irish) to the Southern parts of the country.
It was simply a beautiful map and showed demographic migration patterns clearly, and how they broke down into regional conflicts and so forth. Brilliant piece of work.
I have the link for it somewhere, but it is currently lost in my forest of links. If I can somehow find it, i'll post it because you strike me as the sort of fellow who can grasp complex factors governing the larger picture.