The original question had to be edited down. I think that both works are making a statement that people who are economically challenged are the ones more likely to be excluded from the narrative of the American Dream. On first glance, this appears to be paradoxical. The American Dream is designed to empower those who "have nothing" and strive to "become something." Yet, in both works, there is a distinct statement that there are individuals that have power in the configuration of the American Dream and those who lack it. The individuals who lack power and material prosperity are the ones more likely to be excluded from the American Dream.
In the case of the Younger family, there are forces preventing them from full acknowledgement of their American Dream. Part of this is seen in the Lindner character, who tries to fill them with fear about a move into a neighborhood to make their lives better. Part of this is an economic system in which money and wealth defines power. Walter feels emasculated when the money is stolen from him, "tooken," because without that money he feels a lack of power. In this configuration, those who are without wealth or power is one where such voices are excluded from the American Dream. When Walter speaks of the "takers" and the "tooken," a statement in which those who are poor are left outside of the American Dream.
For Willy, the same configuration exists. The need to "be something" is constructed in strictly material terms. This "matrix" is an overwhelming force because it reaffirms his own lack of value in so many ways. Willy is the kind of person excluded from the narrative of the American Dream because he has appropriated its terms in defining his own chances of success. If he "makes it," in terms of money, he will find success. In this sense of definition, those who lack money and material wealth are not included. It is in this light where both narratives show that being poor results in a sense of marginalization in the American Dream.