Personally, I don't think there's any inherent, substantive differences between members of different 'races' or ethnic groups. I know this is an old trope, but I think it really does boil down to cultural differences and environment. For instance, if you have a black child who was raised by a white, middle-class family, provided that that child doesn't become influenced by the 'gangsta' culture so prevalent in modern times, what you basically end up with is a 'white' person inside a black's body. That child will likely grow up with a greater appreciation for education and a desire to enter the professions. Depending on whether that family was Catholic, though, the child could have other problems, such as an over-attachment to material things (something common to people of all races), or a distorted view of sex and healthy relationships.
Anyway, my point is that race or ethnicity doesn't make any difference, but a person's upbringing and social environment clearly do. I know it can be disheartening when looking at the history of African peoples, but I don't believe that there's any sort of inherent 'defect' in black people or people of other races. Christ died for all of us, and I'm sure He has a plan for all of us, too. Only He knows the reasons why certain peoples have developed along a certain path, but I'm sure He has good reasons. The best thing would be to focus on the present and do our best to try to convert people of all races to the one true Faith.