Estimated Breakdown of "American" Ancestry in the US?

[DINGO Joe]

The county map for "American" is interesting and there must have been some localize efforts to get people to answer that .  Why would Vermillion IL be 20 points more American than the surrounding counties or Buchannon and Tazewell VA 30 pts higher than McDowell WV?  Perhaps the most amusing in Accomack Va, which has a large minority pop (33%) and is famous for it's Tangier Island accent (old English) and still racked up a 40% American designation.

[DINGO Joe]

The last sentence is funny, as there seems to be a correlation between American ancestry and a shift to the Republican party in the last twenty years.

Well, the counties that identify as American are rural, white, poor and uneducated, so there's the correlation.