Are you supposed to draw on literature that you've read in the course? If so, it would help us to know what your professor has had you read.
Also, it would be good to know your own interests. The topic is so wide open that who you are will make a big difference in what you would like to write about. Do you believe in the American Dream or do you feel it to be more of a nightmare? Have you or your ancestors come from another country and done well, in which case you might want to focus on immigrant literature, or were your ancestors among those who were displaced by the European conquest of the Americas, in which case you might want to focus on Native American responses to American Dream literature? Do you see the election of Barack Obama as proof of the reality of the American Dream, in which case you could focus on literature with a civil rights theme? Do you feel alienated from American culture, in which case you might want to focus on literature that portrays America as a dystopia in which citizens are seduced into compliance with consumerism by an illusory dream?
You can see by the range of these examples why we need to know more about you and the books you have read for the course before we can offer concrete suggestions.
Also, please tell us the topics you have considered and rejected, as we may be able to work one of them into something you could use.
Simone, EssayForum.com