> If there's a separation of Church and State, does that mean that we can allow a State to be run by religious zealots?

If the so-called "religious zealots" were duly elected through free and fair democratic process, then yes absolutely. The "separation of Church and State" does not mean "secularism", it means religious pluralism, with no favorites for a particular religion. The absence of religious belief is not "neutral" but instead just another belief system, and all belief systems are treated equally. This is why we don't administer religious tests to enter office, which allows atheists to enter office, but (importantly) also allows religious people to enter office regardless of their faith. All that said, the Constitution disallows religious zealots from explicitly codifying religious scripture into the legal process or from establishing a state religion.

> What if Afghanistan were a state?

Afghanistan's problems stem from 1) the fact their religious zealots have taken over the country by force rather than via free and fair elections and 2) the fact that they have an officially established state religion that explicitly operates on Sharia law.

> Would our nation allow them to stone harlots, and behead adulterers?

It would not, but that's not because of some abstract commitment to secularism, but because that would likely violate the 8th Amendment which proscribes cruel and unusual punishments. In fact, the Constitution likely permits States from outlawing adultery if their citizens so desire. One might choose to support such laws because they think "cheating is bad", but it doesn't matter which book made them think that "cheating is bad". The Constitution places guard rails on which human rights may not be violated — and unfortunately abortion isn't one of those human rights enshrined in the Constitution.

> Let's face it: The right of women to privacy, life, and happiness runs directly afoul of a religious belief (not shared by all religions, not even by Christianity, Judaism, or the bible, only Christianists) in the theoretical life of unborn children. Who but the mother is best suited to choose the right balance of rights?

Again, one's opinion on how society should choose the right balance of rights is a function of the core belief system they operate off of. One may derive their belief system from secular sources, like reading Harry Potter as a child or being raised a particular way, or from religious sources like the Bible or the Quran. "Separation of church and state" does not mean that the government cannot regulate behavior based on religious beliefs, it just means that the State cannot establish a state religion.

In Islam, gambling is a sin, and one may choose to personally vote to outlaw gambling because they are Muslim, but that doesn't mean that outlawing gambling is a violate of "separation of Church and State". It doesn't matter what people's reasons are for voting a particular way, as long as the end result is otherwise permissible.

As it relates to abortion, yes you're correct that the majority of pro-lifers are religious, and likely derive their views on abortion from non-secular belief systems, but there are also many secular pro-lifers (https://www.loc.gov/item/lcwaN0018333/), even Jewish, Hindu, and Muslim pro-lifers (https://www.pewresearch.org/religion/religious-landscape-stu...). Even though they're in the minority among their respective groups, they apply some belief system to derive their moral views, and then use those moral views while participating in democracy. Again, it does not matter what people's reasons are for voting a particular way, as long as the end result is otherwise permissible. Conversely, if one's religious beliefs were that "free speech is bad", and they attempted to vote to regulate speech based off of their personal beliefs, the Constitution would invalidate any laws that came about that way because the end result is not permissible by the Bill of Rights.

I personally agree with you that the mother is best suited to choose the balance of rights, but that's because I (probably) derive my morals off of a similar set of core beliefs as you do, and therefore we are able to agree on the issue of abortion. The fact that this is not true for everybody is not a violation of "separation of Church and State", and is to be expected in a religiously pluralistic country.