How does the setting in The Road serve as the main antagonist?
The road in Cormac McCarthy's The Road is the enemy. It is the obstacle more than it is their path. The setting of the story, a post-apocalyptic Earth with few remaining humans (and hostile, animalistic ones at that), is trying to kill the man and his son continually. Forest fires, cannibals, a nagging lung disease the father has, the long journey they have along with the unknowns at even their destination all make for a setting that is inherently antagonistic and hostile.
Were it not for that setting, they could find food and water more easily, they could find their way perhaps to something like safety, or have any chance at a more stable society, but the hostile environment has driven all of humanity nearer to the edge that the man and boy face.