In his new book, “Fall,” the celebrated sci-fi author Neal Stephenson envisions a future United States split between the violent, gun-toting, uneducated, cross-burning religious fanatics of bullet-ridden “Ameristan” and the peaceful, educated, secular denizens of the nation’s Blue enclaves, where decorum and truth always prevail. Stephenson, one of the most imaginative novelists of our time, fails to live up to his usual standards with “Fall.” Cultural and political elites have long depicted a Red America teeming with slack-jawed extremists; there is nothing original about his vision. In fact, it isn’t very far removed from the perception many coastal elites hold...