For decades, Americans were vaguely aware that Islamist barbarians were in the deserts of the Middle East and in the mountains of Afghanistan and Pakistan, executing "infidels" and raiding villages with unrecognizable names. But the Muslim world seemed far away, remote, and irrelevant to our daily lives. Then came the terrorist attacks of 9/11, followed by attacks at Fort Hood, the Boston Marathon, San Bernardino, and more. Now terrorists seem to...