Is there a concept of Christian State in Christianity? In some of my other questions, I have read that State and church are kept separate in Christianity. I am curious to know, is there any concept of Christian state where Biblical laws and doctrines are enforced or facilitated? Or simply Christians are never supposed to strive for a Christian state?
Christianity does not hold a "church and state must be separate" view at all; that might be part of the US constitution, but : not universal - and to all intents and purposes it is not even correct in the US, since it is quietly acknowledged that you don't stand much chance of election if you are openly non-Christian (regardless of your actual views). Indeed, there are still several US states that have, as part of their state constitution, that you can't hold office unless you believe in God (to all intents and purposes, the Christian God). OK, that sounds like a technicality, until people actually try to enforce it.

Now, let's step away from the US, and look at Europe; there are plenty of places in Europe that have an established church. Which is to say: the church that is officially recognised and has power. In England, the Church of England held massive power, and it is only recently waning - but even so, the C of E has unelected bishops that have an automatic place in the highest assembly in the land. That does not sound like separation. This is mirrored in a number of other countries, where the church holds not just social influence, but genuine political power. Historically, this power was put to direct use, often to suppress and enforce the religious statutes of the time. Heresy and blasphemy have been beaten down with sticks and pyres.

My point: the premise of the question is incorrect. Whether Christianity "demands" a separation between church and state seems largely a point of interpretation; for many, the "render unto Caesar" view (i.e. separation) is adopted, but conversely Christians of various ilks have worked hard to try to bring about such a state.