Well then, maybe it's time to take things a little further, and talk about the foundation of America's law being based upon God's laws in The Bible?
I for one hate what politics has become, but what politics is really about is creating and changing laws that affect us. I personally am very concerned when our elected officials introduce legislation that goes against our U.S. Constitution and Bill of Rights, and our inalienable rights from God.
God's people must have a law, otherwise we would be lawless, which is how the wicked want to live in creating chaos and evil around us. All Christians should be concerned about those things. As U.S. citizens, we have a duty to be concerned about that, because our system of government is not like other nations of history. Ours was designed for us to take part.
What our Lord Jesus said about rendering unto Casear what belongs to Casear, and to God what belongs to God, is a moot point on this matter. Why? It's because He showed us His first coming was not to take rule over the nations with a rod of iron, but to die on the cross. He said He didn't come to bring peace, but division. He said if His Kingdom was of that time, then His servants would have fought to prevent His crucifixion.
As Christians, it's not our job to force Christianity upon those who don't want it. But it is our duty to suggest laws that follows the way God wants us to live, so not only that we may enjoy peace and prosperity of His blessing, but also that the unbelieving may enjoy that also, and by that example their possibly seeing that difference and coming to Christ. Christians can have that influence in politics without putting the label Christian upon it.
For whatever reason, many of God's people in America have gotten away from understanding what God's laws are about. It's not by accident that inside the U.S. Supreme Court building in D.C. it has wood carvings of Moses holding tablets which represent God's giving of His Ten Commandments. The first four commandments are primarily spiritual involving our relationship with God of The Bible. But the last six concern mostly how we treat each other, which is covered withn our civil law system still today.
I think our U.S. judicial system by the founders, by limits of the U.S. Constitution in regard to religion, was doomed for failure in protecting our nation as a Christian nation by not covering the first four of the Ten Commandments under judicial process. The founders instead allowed that corner to remain open because of not wanting to create another theocratic state where corrupt Church leaders could persecute our religious freedom, a major issue which the early founders of the American colonies never forgot with their escape from religious corruptions in European Church/State governments.
So our judicial system was reduced to protecting the order of civil law which involves the last six commandments (how we treat each other), while allowing us freedom to worship whatever we want.
Our nation in its early history actually DID make laws that supported Christianity and the following of the first four commandments, even some communities making it a law requirement to attend a Church on Sunday (Blue laws). Some counties in the U.S. still won't allow the selling of alchohol on Sundays, and limit the amount of business done on Sunday. But little by little, the "crept in unawares" have found out our Constitution does not support government promoting laws involving religious belief. The first ammendment states the government shall make no law promoting religion; but also will not prohibit its free excercise.
That has opened America up to allowing every kind of religious belief on earth to come here. The only way I see our nation could limit the number of religions coming into our country is by limiting immigration. That still wouldn't stop born U.S. citizens from bringing other religious beliefs back to America via travels to foreign nations.
I think our early U.S. Constitutional founders understood what they were doing, and also understood the problems that might come by not defining Christianity as the only allowed religious freedom. They only assumed that we would remain a Christian nation, as that is what the majority then followed. The real key is what the 'majority' follow still today. If the majority of U.S. citizens want our nation to be a Christian nation, then our U.S. Constitution protects U.S. citizens right to that. But it must be by consent of the majority, and not by rule of law. That is what makes the U.S. different from other nations, especially nations where the religion is head of the state (like Islamic countries, and some old Catholic countries).
What can we say then? Should we the people change the 1st Ammendment to state that government will only promote Christianity and no other religion, while allowing free exercise of religious freedom at the same time? (I'm a Christian by the way). We would fast become a theocratic Church state if that was done. I think all Christians (myself) wouldn't mind that to some degree, as long as it didn't force Christianity upon the unbelieving against their will. But I don't see how that would happen. The unbelieving could be put under the rule of law to follow Christian doctrine while they followed something else in privacy of their home.
What is the answer then?
There's only one me thinks; it is the future Monarchy reign of our Lord Jesus Christ, our KING. A monarchy truly is absolute rule. And if the monarch is perfectly righteous, and spreads righteousness to the people, then there is no better system of government to be under. But if the monarch is wicked, there's no worse type of government over the people. Many of God's people have learned that firsthand in previous generations (my ancestors from Euroope included). Under a righteous monarch, without a parliamentary system to get in the way, but with righteous governors, much of the bickering by politicians we see today wouldn't exist.
Yet I love my country of the United States of America, so don't get me wrong. All I'm doing is pointing out how much we NEED our Lord Jesus King of Righteousness, for no man can be a perfect ruler today. That's why even the most advanced government system on earth today (our U.S. Constitutional Republic) has also fallen short of the glory and righteousness of Christ's future Monarchy reign, and it will continue to do so.