As the question is posed, it seems to suggest that the American Dream can be represented as a key that can open the door of freedom and opportunity to an individual. As a key, the American Dream is only the initial stage offering an individual the chance to become a better person and to be successful at worthwhile ventures and goals.
F. Scott Fitzgerald's The Great Gatsby depicts what can happen when the perception of the American Dream becomes distorted by false goals such as the acquistion of wealth and social position as a measure of success and status. People become corrupted in their selfishness and illusions, and, thus, derive no true satisfaction in life because of their corrosion of values. Truly, these people become moral failures as their lives are but " the service of a vast, vulgar and meretricious beauty."
In the final chapter, Nick describes these people corrupted by their materialistic American Dream:
They were careless people...they smashed tup things and creatures and then retreated back into their money or their vast carelessness....
Once a person obtains the key to freedom to pursue his dreams, he must choose the correct door that opens to those values and goals that are, indeed, worthy, and not illusory or only materialistic.