Eleven years ago, Illinois Senator Barack Obama delivered the keynote address at a conference sponsored by Sojourners, the self-styled “progressive” Christian magazine. “Whatever we once were, we are no longer a Christian nation,” said the future 44th president. America was also “a Jewish nation, a Muslim nation, a Buddhist nation, and a Hindu nation, and a nation of unbelievers.” That’s the distorted view of America’s religiosity Mr. Obama brought with him to the White House. And he was dead wrong. America is, indisputably, a Christian nation. And that was confirmed this past week by the Pew Research Center, which released...