Because of racist laws, policies and practices Black people have fewer opportunities from literally before they're born. Studies indicate that poor nutrition and other environmental factors explain the "IQ gap" nearly completely. The remaining points are most likely an issue of bias in the tests themselves. Most white people wouldn't do well in an AAVE based IQ test.

Black people (and other minorities) are being actively discriminated against. In terms of the neighborhoods they live in (white flight), law enforcement (stop and frisk, minimum sentences, racial profiling), employment, housing (mortgage applications) and so on. This active discrimination is an ongoing and constant problem that goes all the way back to apartheid. Black people will do better when white people stop holding them back.

Conflating black culture and active discrimination has racist connotations. For instance appalling Wall Street behavior is not condemned as a failing of white culture, but street crime is erroneously attributed as a failing of black culture. There are a thousand other examples. Black culture: music, food, dance, art, speech are not to blame. No more than white culture is to blame for WW2.

It's part of the racist discourse where environmental factors are described as if they're innate failings of people who are genetically no different from anybody else.

Now I don't believe you're a racist person (you probably don't think group X is inferior to group Y), but the arguments you make have racist connotations for the reasons I gave above.