It should be remembered that there is a big gap (over a 100 years) between the ending of the slave trade (as against slavery) and the 1920s and 30s.

Although officially the importation of African slaves was made illegal in 1808, it carried on as late as 1840 (see this timeline). The 13th Amendment to the U.S. Constitution was ratified in December 1865. The parents and grandparents of African Americans making music the 1920's had (in many cases) been slaves. Consider how close the reality of World War II and the Holocaust are to our lives today. That's how close the Civil War and slavery were to the '20s. And, that's ignoring the next 50+ years of tribulation which did not end with the end of legal slavery and enforced the retention of a distinct culture.

I'm pretty much an ignoramus about the blues, but it really has struck me recently how close the experience of slavery -- and by extension, African roots as held in an enforced subculture -- was to people in the early 20th century.

This is not to contradict your point that the blues shouldn't be seen as lifted intact from Africa, just to bring it a little closer.

~ Becky in Tucson