Of course, African Americans have only come to have relatively full political equality in the US since the 1960s. It was only with the Voting Rights Act of 1965 that the black right to vote (in the South, at least) has been fully realized. It is hard to pin down and agree on exactly how political equality has impacted black society.
One impact that is indisputable is that political equality has allowed many more African Americans to take positions of power in government. The most obvious of these is, of course, Pres. Obama, but many other African Americans hold and have held lower offices. This generally helps to get Americans used to the idea of African Americans in positions of power and responsibility. This has (arguably) improved the image of black people in the minds of other Americans.
What is much more debateable is how much good political equality has done to the average African American. The law encyclopedia link below argues, for example, that
Many politicians who formerly made overt appeals to white supremacy tempered their racist rhetoric to draw support from new black voters.
This seems to be true, but it is not clear that this change has led to any tangible benefits for the black community. It is not clear that it has led to government policies today that are more favorable towards the black community than they were in for example, the late 1960s.