In the United States, idk. In North America, Scandinavians. In the Caribbean/South America the Spanish.
Spanish and Portuguese, most likely.
The White Southern slavers were mostly English, Irish and German?
If you look at this Ancestry map, most of the South is colored in Blue, meaning "American". What defines American?
https://www.thecinyc.com/2013-17-ahr-multimap
Its a recently added census choice, that has become the preferred option for a lot of whites of mixed (often British) ancestry, as well as a number of people of Scots-Irish and Scottish ancestry.
