> Where does culture enter into this?
For one you cite a phenomenon that was unique to a certain time/place (the irish).
> The point is that whiteness in America isn't a race at all; it's a social construction
My objection is how this misses the forest for the trees. There's a weak correlation between some rednecks in appalachia who hate blacks and, say, the hiring behaviour of wealthy whites in business, or the politics driven out of middle-class America which push out ineffective criminal justice policy.
These need to be confronted on a culture-by-culture basis.
For example, just look at how so many people with honest concern about violence in ghettos often blame it on the black race, or because of the popularity of the former, non-racists who criticize it will get dismissed as merely being racists. But just because they are primarily black doesn't mean the problem is racial nor does it mean their race is entirely why they got into that position. There are plenty of non-black ghettos with high violence and low educations in many countries.
If you lump it all into a racial issue you will only get a huge push back as we see here in this thread. For good reasons too, it's as reductive and irrational as the racists or anti-semites.
You could get all social-science academia about it, but all cultures are partially social constructs. And pretending it's only a social construction is similarly reductive, there is more than enough resesrch on the genetic S culture.