The question of whether the Founders envisioned the United States as a Christian nation is far from clear. Documents can be trotted out supporting both sides of the issue, although it would be a mistake to believe that every reference to "God" or "religion" is to be interpreted as Christianity as a 21st century American would recognize it; just as it would be erroneous to believe that the Founders were complete secularists. My own opinion is that the intent was to guarantee that no religion would receive preference and that no religion would be persecuted. With a few exceptions such as Judaism, religion among the descendants of Europeans was equated with Christianity. Islam and the Asian religions were considered foreign and exotic and Native American religions were beneath contempt. It was viewed as enlightened to look at even Catholics as of worthy of equal rights as Protestants.
For the purposes of argument, let's assume that the Founders actually viewed the United States as a Christian nation and wanted it that way. Is that a good argument for keeping it that way? Sometimes we view the Founders as demi-gods whose wisdom brought order to chaos and caused the sun to rise. But consider that the Founders countenanced slavery, women had virtually no rights, native peoples were not "people" and the vote was confined to white, male landowners. In others words, our culture has changed and the way that the Constitution has been interpreted has changed with it. The United States of the 1790's is very different from the United States of the 2010's. The principle that there should be no preference among Christian denominations must evolve to include
non-Christian groups as well as those who follow no religion at all.
The second main argument used to impose religious beliefs and strictures on everyone is that "the people" want it. The majority don't want a mosque across the street from the rubble of the World Trade Center, the majority don't want gay marriage. For Christians, this works as long as they are in fact the majority. What would their reaction be if they were the minority? Surely they would fall back on Argument #1, but would no longer have Argument #2, the Will of the People to fall back on. What most people do not realize is that we are not an absolute democracy. The will of a majority of the people does not confer legality. We have the Bill of Rights, amendments to the Constitution that guarantee individual liberty no matter what the majority has to say about it. You cannot vote to eliminate freedom of speech, or for the establishment of a particular religion. It doesn't matter if the majority wants it. Now theoretically, we could have a constitutional amendment or constitutional convention that would repeal the First Amendment (or any other part of the Constitution), but that hasn't happened and probably won't. So it doesn't matter that a majority are Christian, they do not have the right or authority to impose their religious views on the rest of us or make laws that conform to their religion if it does not serve an otherwise neutral function. For example, the biblical commandment "Thou Shalt Not Kill" can be written into law, not because Exodus says so, but because it makes good sense and serves the function of maintaining public order and protecting individual rights. On the other hand "Thou Shalt Honor the Sabbath Day and Keep it Holy" cannot be written into law, although for years laws were on the books requiring business to close on Sunday (which is not, by the way, the sabbath).
Finally, what most Christians who support no separation of Church and State, who support laws based on the bible, do not think through, is that the Christians in power under a hypothetical Christian government might not be their kind of Christian. Many Christians, especially some of those on the more fundamentalist side of the spectrum, do not consider some other Christians to be real Christians. For years I was part of a religious organization wherein many members talked about how great it would be if we had godly elected officials. Even then I considered that if we did have a "Christian" government, it would be composed of "them" and not "us". The "them" that considered my kind a dangeroud cult. I was raised a Catholic. Imagine my surprise when I learned later in life that many of the Protestant denomination did not consider me a real Christian. How many people refrained from voting for super-religious Mitt Romney because they thought Mormons weren't Christinas? Consider the situation in many Muslim countries. Many of them were excited to see an Islamic government after decades of secular dictatorship. What they hadn't bargained on was the deep distrust and even hatred that different Muslims had for each other.
So, even if you are a believer, you'd be wise to be skeptical of those politicians who claim to support "God in government"
