I know about most of the instances you are referring to. I just want to point out that everything in the OT you mentioned applied ONLY to the nation/people of Israel because they were ruled by GOD alone in the form of government known as a theocracy. Once the old covenant was ended and the new covenant began, all those rules were more or less null and void.
We could talk about all those laws/rules and why they existed thousands of years ago but that's not the point of this discussion.
You are right to say that the ultimate goal of Christian morality is to be perfect/righteous as GOD is. Isn't perfection a good goal to shoot for?
The thing is, God logically couldn't have changed in the mere thousands of years since all these nasty events - aside from the continued violent behavior in the New Testament (mostly in the book of Revelation, which is notable because Revelation is the only NT book in which God directly communicates and intervenes with the mortal population in a significant way; in every other book, unless I'm having a major memory failure here, God primarily speaks through his "Son" and his followers), it is stated in the Bible that a thousand years is like a day to God. Not only that, but God would have existed for literally an infinite period of time beforehand. Those who believe in the "sacrifice" of Jesus having forgiven all of our sins and God becoming a god of love instead of a god of laws are essentially claiming that in a period of a couple days out of an infinite lifetime, God completely changed his character. It doesn't sound plausible.
There are no laws in the beginning of this country about killing homosexuals or not allowing divorce or anything else and there shouldn't be. There weren't when the nation began and there shouldn't be now - we don't need laws created by a government telling us what to do with our personal lives. But we do need laws created to protect our freedoms and liberties.
The thing is, most Christians (at least those who make Christianity part of their political affiliation, which logically should be all of them, even if it somehow isn't in practice) disagree with you on this; they want the State to essentially be a puppet of the Kingdom of God. And that's terrible.
The 10 commandments were a cornerstone of American morality because they work - you don't murder someone, you don't steal from someone, you don't bear false witness/lie under oath, etc. - personal freedoms and liberties were protected because life and property and religion were sacred to GOD. In America life, property, religion and speech are sacred. You can say what you want and do what you want to a point - and that point is a negative impact on someone else's life, property, religion or speech.
Except that you're leaving out the commandments that aren't the cornerstone of American morality - namely, the remaining seven of them have no basis in law (and at least three are explicitly opposed to the Constitution), and aren't universally considered cornerstones of morality. (Have no other gods before God, do not worship graven images, honor your father and mother, keep the sabbath holy, do not take God's name in vain, do not kill adultery, do not covet)
Personal freedom and liberties are protected because those freedoms are valuable to the PEOPLE. God has no part in it, and in fact God is typically thought of as being opposed to said freedoms.
Of course, now that people are beginning to care less about these freedoms, we see them being eroded.
The system of Christian morality laid out by Christ works great for society - and the beauty of new covenant/Christ law/morality is that it applies ONLY TO THOSE THAT CHOOSE TO SUBMIT TO IT. If you are a Christ follower, you have a longer list of rules to follow than the non-believer.
Those that don't believe in Christ or GOD don't have to follow the extra rules - obviously there are consequences for not following those rules or accepting the grace of Christ - but the consequences of those choices aren't felt in this life, only in the ETERNAL life.
But what does this have to do with the State? Are you arguing in favor of a legal system that distinguishes between Christians and non-Christians, the way Muslim states of old did?
So the idea that Christian morality is currently made up of rules and laws that were created to be temporary and exist only in the special circumstance of thousands of years ago like what you listed is a big misunderstanding and shows a sad trend in the understanding of Christianity by believers and non-believers alike.
The Bible nowhere implies that the Old rules were meant to be temporary, until the heretic Paul arrived on the scene. Jesus himself bluntly said that he did not come to overthrow the Law, but to uphold it. Not a letter was to be struck from the Law, or something like that.
(There was a point where Peter received a vision from God telling him to go forth and eat the unclean animals, but if I remember correctly, this was actually a metaphor telling him to go and preach to the Gentiles. At any rate, the vision would only have invalidated the dietary restrictions at most.)
The Christian morality of the 10 commandments and the new covenant/new testament as explained by Christ and others IS the foundation of our laws and Constitution. The founders didn't transpose the Bible to Bill of Rights and Constitution, but just as the textbooks you read in school help shape your intelligence as an adult, the morality of Christianity shaped the foundation of our country.
Actually, our founding fathers were deists and wanted to get away from religious government (particularly the Church of England). The Treaty of Tripoli explicitly stated that the United States is not a Christian nation, and religious fundamentalism only began to play a permanent, significant role in national politics during the 1970s-80s or so when the Moral Majority gained traction and successfully pushed the demon Reagan into office in 1980.
Besides, something having shaped our country doesn't necessarily make it good. Puritanism, slavery, liberalism, Christianity, capitalism, and immigration also shaped our nation, but not all of those things were good (pretty much everyone today agrees that slavery and Puritanism were bad, and the rest are fiercely debated to no useful end).
