Estimated Breakdown of "American" Ancestry in the US?

[RINO Tom]

According to the US Statistical Atlas, 6.9% of people in the United States self-report their ancestry as simply "American."  I'm not interested in discussing the validity of that (though I favor the perspective that the great American tradition should lead us to not offering that as a choice) but rather am interested in how those people would break down if forced to pick a European ancestry (talking pluralities here, so someone whose largest ancestry component is only 12.5% English would be "English" in this case).  How do you think that this group would roughly break down?  Would the makeup of "American" ancestry be fundamentally different by region and state?  For reference, here are the European ancestries for comparison:

14.4% German
10.4% Irish
7.7% English
5.4% Italian
2.9% Polish
2.6% French
1.7% Scottish

Also, here are the states with the largest reported "American" ancestry (keep in mind the non-White populations in some of these states would affect these numbers ... in other words, Whites in AL might be reporting "American" at higher numbers than KY, considering they're a smaller slice of the whole population):

Kentucky: 18.45%
Tennessee: 15.85%
Alabama: 15.62%
West Virginia: 12.38%
North Carolina: 12.18%
Mississippi: 11.74%
Georgia: 11.71%
South Carolina: 11.58%
Arkansas: 11.01%

Considering the states with the highest ancestries other than American tend to be the most German, Italian or Scandinavian, I would assume that most of these people would be of English, Irish or Sottish/Scots-Irish descent rather than other European ethnicities, no?  In making my own maps, I have always just lumped them in with "English" to simplify things, but I would like to remake a more accurate one.

Any answers are appreciated, and I know we have discussed this before!

[RINO Tom]

I forgot to say this, but thank you to everyone for the awesome responses!  This will help me toy with my map and make it a bit better looking.

[RINO Tom]

For people that have been here many generations, it's the only logical answer for ethnicity on the census form. My dad's family is Scotch-Irish with some Cherokee thrown in. My mom's family is German. What am I supposed to select if given a list of European nationalities? The only sensible selection is "white American". Now throw on top of it I have a couple kids and I have no idea really what my wife's family are beyond "white American" when that is half my kids genetically. You also have people that only follow ethnicity paternally because that's where their surname comes from, so they can make a selection but the selection is probably wrong.

"Scotch-Irish" is a term that's meaningless outside America anyway*, so I'm not convinced that "American" isn't a better designator.

A very few Ulster Protestants will identify as Ulster Scots, but it's a minority pursuit and none of them will use the term 'Scotch-Irish', nor is there very much in common culturally between Ballymena and Appalachia.

No one here uses Ulster Scots. If forced to select something European with a gun to my head, I'd say Scotch-Irish.

Let's not act like picking the ethnicity associated with a surname or picking a plurality is somehow less "accurate" than simply saying "American," haha.