It has become popular to say that certain countries, regions, or cultures are today to be labeled “Post-Christian.” The idea behind this is that in the past, the cultural norms, presumptive beliefs, and government allegiances were tied to Cultural Christianity. I believe I must add the key term “cultural to Christianity since a lot of the hallmarks used to identify Christian have little to do with Fruit of the Spirit, or obeying the Great Commandment. Cultural Christianity is often often tied to issues of government, law, and economics. Frankly, it is hard to say with much confidence what governmental form is Christian. Moses and Joshua led a chiefdom. The Judges like Deborah and Jephthah led a tribal confederacy. David and Hezekiah led a classic monarchy. Zerubbabel and Nehemiah served as provincial governors of a (pagan) empire. The New Testament, frankly, works under the premise that Christians will live under a governmental system that is either hostile or ambivalent to them. Economically, one can read parts of the Bible and believe that God is a Laissez-faire Capitalist, and other places a Laissez-faire Socialist. Much of cultural Christianity deals with things that God is not all that interested, and in some cases actively opposes (noting, to be cautious, that I could be wrong).
It is probably best to say that the Bible supports a Christianity that is counter-cultural with no presumption of control over government or the economy. And that was true before the Emperor Constantine (ignoring Armenia, Adiabene, and Osrhoene). While Constantine did not make Christianity the “law of the land” (others did that later), he did give Christianity status and influence within the Roman Empire. Power was given to Christian leaders that went beyond their own congregations. And by taking on the self-assigned role of Bishop to bishops, Constantine made Christianity as part of the system. So while the Kingdom of God was in opposition to the kingdoms of this world, but the Church was not.
Prior to Constantine (Pre-Constantinian) the church grew despite (or perhaps because of) modest to severe persecution. With Constantine the church grew fast, but the church changed drastically and not necessarily for the best. The symbols of power were taken on by the bishops, and money flowed in from the government. In many ways the empire entered the church far more than the church entered the empire.
From Constantine onward, there were a lot of attempts to link church and state. The United States was one of the first big-scale attempts to separate the two in Western Christianity, followed by the more extreme (first) French Revolution. It was, however, not until the 19th and 20th centuries where Christendom was truly seen as problematic. The Church needs to be protected FROM the government more than it needs to be protected BY the government. Arguably the broader society needs the example of Christians rather than the coercion from Christians.
There is a cost for this link of Church and State. Only a few years ago, January 1, 2000, the government of Sweden formally broke official ties with the Church of Sweden. While the response wasn’t unanimous, it seems like the Church of Sweden rather liked the divorce. The special status the church had also resulted in the government having a fair bit of control over the church leadership and policies. Some members of the leadership of the Church of Sweden appeared to welcome the removal of that control. I am not a Swede by nationality (although my ancestors did come from Sweden) so I don’t know whether the separation was a good thing or not. However, I come from a Free Church tradition that generally sees separation of Church and State as a good thing (although some of my Free Church friends in the US seem to be rethinking that issue a bit lately).
It seems to me that Jesus was always counter-cultural. Some people believe that counter-cultural means anti-cultural. That is far from it. Counter-cultural means to be fully enculturated into a society and stand out in only specific purposeful ways. Jesus was so linked to 1st century Palestine (Judea and Galilee) that He needed to be identified by one of His friends for His arrest. He ate, drank, talked, and socialized like the people of His time. Yet, in certain key ways, His life was a testimony against certain beliefs (even worldview beliefs) in the society in which He resided.
We live in a Post-Constantinian era for the church. We (as in ‘the Church’) no longer have unquestioned sway (in most parts of the world) over government or the broader non-Christian populace.
While I think it is naive to think that one can recapture the past, some different things in the past are better than others. Recapturing Constantinian Christianity is not one we should desire to recapture. Recapturing a Pre-Constantinian (now more appropriately called Post-Constantinian) Christianity I think is a good thing. It should be embraced… welcomed.
Far too often when the church tries to use political power to attempt to solve societal problems, we become part of the problem.