The Judaeo–Christian tradition has had an influence on American political thought from the very beginning. However, Americans have tried to keep any single denomination or tradition from having any advantages or disadvantages over another or any perspective of faith, including atheism.
Jon Meacham’s The Soul of America: The Battle for Our Better Angels and his American Gospel: God, the Founding Fathers, and the Making of a Nation give a much clearer and detailed description of the role and importance of religion in our nation’s founding.
However, Michelle Goldberg’s book points to a disturbing strand of current American religious and political thought, usually found on the religious and political right.
Christian nationalism is the mistaken historical notion that the Founding Fathers intended that the U.S. would be a Christian nation. The Bible and “God’s law” would be the guiding principles. Those things which are sinful should also be illegal and punished as crimes.
Of course, the founders were very familiar with the Bible (and the Greek and Roman classics), but they did not see the U.S. as a “Christian nation.” Thomas Jefferson did not believe Jesus was born of a virgin, was God, or rose from the dead. In fact, he wrote his own New Testament, taking out all of the miracles. He did like most of the moral guidance.
The perspective of these evangelicals includes Christian dominionism. God gave Adam and Eve dominion over the earth. Most major denominations–including Catholicism–understand this to mean that humanity does not own the earth outright. Rather, the earth is for the benefit of all people, and we are to use it in the name of the Lord, the dominus.” We are stewards, not owners. We will give God an accounting of our use of the earth.
The people of whom Goldberg is writing have a different perspective. They believe that the gift of dominion of the earth was lost with original sin. It is given back with baptism. Therefore, Christians (and not those other people, whoever they are) should rule the world.
This perspective has many implications: creationism vs. evolution in public schools, sexual ethics and morality, public funding of social and religious programs, and so forth.
History and theology make a difference! We need to have a clear understanding of what we are about.