While Hiphop certainty is a blight to the minds of black youth , i dont think it can explain the decline of black culture. In reality , black culture was on a decline before hiphop even emerged. I think you can thank Lydon B Johnson and the liberal social welfare programs that he rolled out , and the mass introduction of drugs into the black community ( and the subsequent war on drugs) for the destruction of black culture. I also think that integration played a inadvertent role as well.

But when talking about italian americans , i think assimilation/intermarriage with non italians , destroyed the culture.