Important read: Thomas Sowell in OpinionJournal.
I think Sowell's first premise is interesting and worth thinking about - that southern blacks absorbed redneck culture and brought it north - but I don't follow his second premise - that this is what holds blacks back. I think that cultural factors are one of the reasons African-Americans lose out, but that structural reasons, to do with racial divisions in the housing market and labor market in the post-slavery years. So, I might like to read Thomas Sowell alongside Thomas Sugrue.
On redneck culture, Sowell argues that it was formed before the whites got into boats to cross the Atlantic. This is obviously partly true, but needs to be complicated a little. Australia's white population came from the same roots, but white Australians perform well educationally, so you need more than the culture to explain it - for example, the plantation system, the relationship between the agrarian South and the industrial North.
Similarly, Sowell is right to draw attention to the historic economic disparities between southern and northern whites. But again, culture can't be the main factor. The difference between an agrarian economy and an industrial economy is also key. He also doesn't speak about the huge disparities *within* the white population of the North.
Sowell's arguments have some relevance to the British case, and the emergence of what is seen as a new poor white underclass. In Britain's cities, white working class boys do worse educationally than any non-white ethnic group, enter worse jobs, are less likely to end with any job. This is something that needs thinking about, and perhaps Sowell offers some help in doing so, but probably only on half of the story.