Massive investments in black communities. Comparing the treatment of the Irish to 400 years of institutionalized chattel slavery is absurd on its face. Also, again, ignoring everything else I mentioned. Some books you should check out to learn more about this. The New Jim Crow and The Color of Money. Black communities have been chronically underfunded, underserved, over-policed, and segregated for the entire history of our country.
Occam would likely object to being left out of the conversation. Perhaps there's a more obvious reason for some of the differences in our society.
Without going into too much detail, consider that the millennial generation of African Americans is the first generation in the country's history to be granted full citizenship rights at birth. (The beginning of Gen X was born into a legally segregated society.) Might that have an impact? If you do not believe the impact is material, it would be reasonable to ask you to explain why.