This issue is now a legacy of the "war on poverty/great society", not of slavery, nor of racism. Entire books have been written on the evidence proving that. See "Conquest and Cultures" (or many free online columns) by Thomas Sowell, raised by a single mother housemaid, yet a non-affirmative action Harvard graduate in 1958.
The murder rate among blacks in 1960 was half of what is was in 1980. In 1960 the vast majority of black children were raised in two-parent households. By 1990 the majority were being raised by single parents. Those changes aren't a legacy of slavery.
Also, racism doesn't explain why black immigrants are so much more successful than native blacks, or why even when there is official racism against certain Asian groups in a country, they still do better in that country. Culture does. A racist in a school situation or a job interview, just judging based on skin color, can't tell what country your parents came from, but your behavior is influence by their culture.
We tend to look at current American black issues and ascribe them to the results of slavery, but the fact is that effects of slavery and life for blacks were getting better for almost 100 years, then suddenly many things some people like to ascribe to the legacy of slavery started to have progress slow down and then began getting worse. It makes no logical sense that the impact of slavery on black family unity would suddenly begin to make things worse 100 years later, but not before that.