We also hear that the USA was founded "as a Christian country," and I remember hearing a talk from someone who believed that had the authors of the U.S. Constitution made it clear that this country was "Christian," that somehow things would be different today. That really is nonsense; for that matter, a number of European countries at one time officially were "Christian" nations, and today none of those things matter, as no place in the world is as secular as Europe today.
However, the connection between historical Christianity and the effect it should have upon the actions of those that govern us was changed permanently in the United States during the 19th Century, first with Unitarianism and then with Progressivism. The political actions of both liberal and conservative "evangelicals" today are reflective of the secular, state-embracing political philosophies that rose during the 1800s and early 1900s, not the Christianity that was practiced by the Early Church, and certainly not of the Bible.
I cannot emphasize that point enough. When American evangelicals launch campaigns to deal with attempts to outlaw the "under God" portion of the Pledge of Allegiance, they are not preserving religious freedom, nor are not paying homage to the ideals of liberty that inspired many of the founders of this nation. Instead, they are endorsing a pledge created by a socialist who despised the founders of this country and who hated the views that the framers of the U.S. Constitution had on law and the state. Indeed, the Pledge of Allegiance is the antithesis of all of those ideals upon which conservative evangelicals claim to be supporting and it is collectivist and Progressivist to the core. Yet, because it has the phrase "under God," Christians are willing to engage in what only can be idolatry and pledge their troth to another god.
Having grown up in the conservative evangelical subculture and still being part of it, I have picked up some insights as to why people who believe in God and who hold to the inerrancy of the Bible have sold out to the State. The answers are more complicated and nuanced than one might expect to read in a publication like the New York Times, which treats evangelicals as though they were alien invaders who have no right even to exist in our society.
Because I am dealing with the modern evangelicals, I will not cover the influence of the Unitarians of the 19th Century, except to say that they were part of nearly every major advancement of State power, including the public school movement in Massachusetts, and the Civil War. Certainly, by the end of the 1800s, the Unitarian influence began to wane, as theological liberalism took hold in the major Protestant denominations.