holy crap- that's a hard one
i assume the artist is commenting on the role of black americans in the 'forging of an American democracy'
you need to talk about the isolation of the black person, and the homogenous nature (through colour) of all the other figure in the picture.
also- the position of the figures, esp. the central figure and those to the right, the central figues orientation to the other figures, stance, etc.
is this a multi media artwork? I can't tell from the image. if it is, you need to talk about it id depth- the process of an art works construction is also a process of constructing meaning in an art work. i can't remember who said that, but whatever movement the artist belongs to, you have to make reference to. you also will need to find an art critic who has written about this art work to back up your arguments