Tell me why I'm wrong. Maybe I don't understand the point you're trying to make.
Are you saying because most American blacks are descended from slaves they get some sort of special understanding not available to other ethnicities? When do you suggest they start being treated like other Americans and expected to pull their weight without excessive gov. assistance?
OK, in no particular order of importance, how slavery of Africans differed from slavery of Europeans:
1. Black people are visibly distinct from Asians, Indians, Europeans. This has allowed for much more definitive segregation, voluntarily and not, over time. I don't think it's possible to understate how significant that was. The Irish/Germans/Poles/Swedes/Italians etc., could after a generation or two, blend completely into American society. Anglicizing their names didn't work for black Americans.
2. Extend period of slavery destroyed much of the family and hierarchical system of black society in America.
3. Black society was developing nicely in the less than 100 years since emancipation and adapting well to the American experiment.
4. LBJ and Teddy Kennedy's Great Society experiment has done several things:
a. It has reduced the number of black people moving into the middle class
b. It again destroyed the family and social structure in black areas, and arguably did so even more effectively than slavery did. We can see similar destruction in some white ethnic groups, such as much of Appalachia. This is another example:
http://www.gopbriefingroom.com/index.php/topic,356328.msg1947479.html#msg19474795. Now, this one is my theory, and I'm still working on it, but I think a good case that stone age people brought suddenly into a modern society generally do poorly. There are examples all over the world. That is separate and in addition to the points above.