For most of U.S. history, Americans were Christian nationalists. Or were they?

I hear a lot of people talking about “Christian nationalism” these days, but I don’t hear a lot of deep historical thinking on the subject. In the first four chapters of my book Was America Founded as a Christian Nation?, I suggested that nearly everyone believed that the United States was a Christian nation. I am not sure this makes them “Christian nationalists” as some define it today, but everyone from abolitionists to liberal Protestants and social gospelers to civil rights activists believed America was a Christian nation.

The following people believed that the United States was a Christian nation: Philip Schaff, John Adams, most Federalists, Lyman Beecher, most of the early historians of the American Revolution (David Ramsey, Mercy Otis Warren, George Bancroft), most early textbook authors (Charles Goodrich, Emma Willard, Noah Webster, Mason Locke Weems, William McGuffey), Horace Bushnell, Frederick Douglass, Albert Barnes, William Lloyd Garrison, Robert Dabney, James Henry Thornwell, the National Reform Association, A.A. Hodge, Charles Blanchard, Billy Sunday, William Jennings Bryan, Henry Ward Beecher, Washington Gladden, Walter Rauschenbush, the Federal Council of Churches, Woodrow Wilson, Rudyard Kipling, the National Association of Evangelicals, Billy Graham, Carl F.H. Henry, Charles Clayton Morrison (editor of the Christian Century), Pope Leo XIII, Martin Luther King Jr., Francis Schaeffer, Phyllis Schafly, David Barton, D. James Kennedy, and Peter Marshall and David Manuel.

Are those who today use the phrase “Christian nationalism” describing something that has been present since the birth of the republic? Or are they describing something that was born in the context of the 1970s?