German ancestry is #1, English ancestry is #2

[Roll Roons]

While most Southern whites are primarily of English descent, I've heard that the more educated ones specifically identify as "English" while less educated ones identify "American".

For instance, Williamson County, TN is by far the most college-educated county in the state and also the only one where a plurality of residents specifically identify as English as opposed to American. Is there something distinct about the ancestry of people living in that particular county? I don't think so.

It's just one data point, but it's something to consider.

[Roll Roons]

Most common last names by state:

https://blogs.ancestry.com/cm/whats-the-most-popular-surname-in-your-state/

Interestingly no German surnames show up in the top three in any state, not even in Wisconsin.  Besides the obvious Spanish dominance in California, Texas and the Southwest, and Asians in Hawaii - you see a few ethnic identifiers (Sullivan in Massachusetts, Olson in North Dakota, more Johnsons and Andersons in the Upper Midwest).

Reading up on this it seems it's because names were spelled in many different ways, that or, less often they were Anglicized like Busch to Bush to Braun to Brown

Anglicized surnames may be more common than you'd think. In the Midwest/Plains states, I wouldn't be surprised if a lot of the Smiths were originally Schmidt and the Millers were originally Mueller.

A lot of these people probably changed their names either at Ellis Island or when the US entered WWI.