I think that Wainwright's fundamental purpose on Changez's development is in his implied suggestion that cultural differences can be overcome. To a great extent, Wainwright has overcome his own cultural differences. He is a man of color, and yet he does not let this define him. To Changez, who is struggling with his own notion of identity at the outset of the narrative, Wainwright represents a model of how he can be. This is where he holds the most amount of influence on Changez.
Wainwright transcends culture, or at least in his mind does so, in his quoting of movie lines, and in his ability to interact freely with others. When he seizes the dance floor at Jim's party, it is a moment where Changez sees what can be for himself. Wainwright has chosen a mode of identity where cultural differences do not define one's sense of self. There was a point in the early frames of the narrative, prior to September 11, where Changez might have embraced this position. In consistency with Changez's fundamental reluctance that is a part of his character, Wainwright's hold on him is a presentation of what might be, a world in which a person of color can transcend and overcome culture. As long as one is willing to forego deep and introspective analysis about themselves and their place within cultural identity, happiness can be present. For Changez, this is alluring, something that is tempting to him and in the days prior to September 11 and his reaction to it, something that presents the hope of totality in a world where there it does not seem to exist.