The “rattlers in your nightmares” are a metaphor for (in desert run)
the public’s fear of traitors
all things that scare people
the nation’s guilty conscience
the fear of snakes

The correct answer for the question that is being presented above is this one: "The nation’s guilty conscience." The “rattlers in your nightmares” are a metaphor for the nation’s guilty conscience. (in Desert Run). "Rattlers in your nightmares" refers to the guilty of the nations.