You seem to believe that in your face conservative white evangelical Protestants are the only Christians. This speaks more to your own biases than society’s.
Every poll of Americans and religions shows Christianity as by far the most popular choice. There is simply no way to square your idea that nonreligious is the default when over 70% of Americans identify as Christian.[0]
As for representation, I have no way verifying this, but I suspect there are more Roman Catholic characters in American film and television than conservative white evangelicals Protestants. If for no other reason than mass, iconography, and religious tchotchkes photography well. Hell, Catholics have the entire horror genre on lock. WEPs have what? Footloose?