How do Of Mice and Men and Death of a Salesman show hopelessness and failure of the American dream?

Both John Steinbeck's novella Of Mice and Men and Arthur Miller's play The Death of a Salesman feature strong, cynical representations of the American Dream. More specifically, many scholars' analyses of the two works believe that each author worked to reveal the death of the American dream through the rise and fall of their respective protagonists. 

In Of Mice and Men, protagonists Lennie and George dream of living on a farm. The novella is set in Depression era America, which lends itself to the downtrodden nature of the characters as well as the fundamental importance of hope and dreams in their survival. Likewise, Death of a Salesman's lead Willy Loman is nearing the end of his career and desperately grasping at the remnants of his youthful dreams. 

In the end, neither story ends with the ultimate success of its protagonist. Instead, all three men's dreams are trampled by circumstance, their own choices, and elements beyond their control. As such, both works are often used to discuss the hopelessness and failure as it relates to the American Dream.