Well, first off there's the fact that you're not going to be elected if you're not a Christian, for a variety of reasons, so pretty much everyone has to pay lip service to the faith regardless of their beliefs. In some cases this goes well beyond "I'm a Christian but that's not how I'll govern"; Rick Santorum, a Republican presidential nominee, said that our nation's values “are based on Biblical truth… And, those truths don’t change just because people’s attitudes may change.” He used this as his basis for opposing same-sex marriage.
Second, there are a ton of laws that are inspired by religion, if not overtly religious themselves. Look at the number of places that don't serve alcohol on Sundays, for instance; there's no secular reason to do that, but most Christian sects keep Sunday as their holy day so there's all sorts of religious reasons. There are also numerous laws regarding abortion, homosexuality, etc, that are pushed the way they are because of religious beliefs. Oklahoma's new "A woman must get the man's permission in order to get an abortion" isn't overtly religious, but there is no possible way that law had any origin other than Christians trying to force others to live the way they want them to live, for instance. (They can't actually outlaw abortion, so they're doing what they can within the confines of [I]Roe v. Wade/I]).
*shrug* You're not going to find a law that says "You must live by Christian rules." There are plenty of cities and states, however, that have enforced that in their laws, and in ways that have nothing to do with nigh-universal rules such such as "don't kill or steal".
Religion is not necessary for those laws, though that perspective is one commonly held by the religious (I can't tell you the number of people who've told me I cannot possibly have morals, nevermind that I'm not even an atheist, simply not a Christian.) Imposing laws does not require religion, and if you need to scare people into obedience there are plenty of ways to do that without invoking God. Many philosophers have arrived at similar conclusions without using religion to get there.Religion was making all the discoveries in the middle ages, because they had the money. They built universities and funded scholars.
Even the psychological aspect of being at ease with death because you believe there's a heaven helps people.
Then there's the moral laws like '' don't steal '' '' don't fuck anyone but your spouse '' which had their purpose.
You think having laws against cheating is a bad thing? It's not. Some humans are animals with no morals. Better to impose them than to let them run rampant.
(And even in your statements, "don't fuck anyone but your spouse" is very much a subjective position. I know people that willingly have an open marriage; they love each other, but are not physically exclusive with one another. The couple I know is incredibly loving and I have no doubts that they will remain married until their death, but from your statement here they're immoral people because they don't live by the Christian view of marriage, regardless of what else they do in their lives.)
Religion did make all (or at least most of) the discoveries in the middle ages. There were a lot of reasons for that, including the fact that they truly believed in a quest for truth, and believed anything they did as part of that quest would ultimately help both science and faith.
However, we don't need to rely on religious institutions to preserve knowledge these days, and they aren't the only ones seeking truth. Indeed, many such institutions now oppose a quest for truth, preferring to push their own vision of the world (see: Creationism, that denies all scientific evidence that directly contradicts their views). The Catholic Church and the Roman Inquisition found Galileo guilty of heresy in 1633 for believing that the Earth was not the center of the universe, something they did not admit fault in or apologize for until 1992.
I do not believe that religion in the past was inherently harmful; many of those who followed religion were simultaneously seeks of truth and justice, and did many great things. Modern religion, however, more and more is demonstrating a desire not to push humanity forward, but to hold it back. Saudi Arabia is an extreme example of that, but not the only one.