I note that whichever side is being put forward with vigor tends strongly to accuse its opposition of being absolutist. Those who say that cultural support is largely irrelevant, because all is the work of the Holy Spirit, seem quite certain that the rest of Christianity is just chockablock full of folks who insist that political power is necessary for the spread of the Gospel.
I have never met or read any Christian who maintains it is absolutely necessary. None. Who are these opponents they rail against? Similarly, those who advocate that creating cultural support for Christian living is a good thing and means we should vote for people who will by-golly do that seem to also claim that those Other Christians who don't get on board care nothing for our supportive American culture and are willing to just let everything go to hell. (There's a subtler liberal version of this, but for this discussion it's simpler to just stick with the unsubtle conservative version.)
Yeah, I don't know any of those, either.
Everyone knows that the work of thoughtful believers and the work of the Holy Spirit are not easy to separate even in theory, let alone in real time. All that remains is to examine ourselves for which way we lean and see if our actions do indeed accord with our theology on the matter.
Some points of interest: CS Lewis notes that England maintained Christian forms for over a century past identifiable markers that it had largely ceased to believe central Christian doctrines. In Dickens's A Christmas Carol, there is only one fleeting mention of Christ, and that not even by name. Some Christian virtues are applauded, particularly generosity, but the whole charming tale revolves around very English pagan spirits convincing Scrooge not to be miserly. Ebenezer's redemption seems to be that he is generous to one employee's family and becomes jolly, full of bonhommy (French word meaning "bonhommy.")
And for ever afterwards, it was always said of him that he knew how to keep Christmas well - as well as any man has ever kept it.Well, there you are then. What more does Christ ask of us, eh? Lewis traces this back further, to Sir Walter Scott and others.
It was not merely that literary figures were playing with such secularised faiths, but that their works were so entirely acceptable and popular. The culture embraced this, swallowed it, without noticing their religion had been drained of its most important meanings. It marks a culture Christian more in name than practice. And yet - Christian virtues were not abandoned, many are still not abandoned, even unto the present day.
It is widely claimed that the Church grows under persecution, its members particularly strong and productive. The earliest Church is given as an example, but I don't think the evidence is strong. The Church grew greatly at first in each new place it was introduced - from 0% to a few percent right off the bat. If we move from those numbers to the percentage who were Christian just before the persecutions ended in the early 4th C and compute backward, we see that the Church in the Roman Empire grew at about 1% a year. The miracle of compound interest and all that. But not much of an advert for persecution being a strategy. It might be good for us personally, but there's no evidence it's good for numbers.
Nor do the modern examples of Russian Pentecostals and Romanian Baptists offer much evidence. The Church survived in those countries, but not everywhere. When the walls came down, there were whole regions in Russia with no evangelical believers anywhere, and not many even of the Orthodox Church, with its solid historical roots. There is no cultural support for Christianity in Japan, and there are no Christians. There is cultural support in South Korea and there are lots of Christians. China had an underground Church that seemed to have grown greatly. But they've also got well over a billion people there and everything grew greatly.
Sometimes when governments get rid of the Christians they are just gone. Sometimes God chooses to do something miraculous instead. Mostly, it's a mixture of the two. I don't see that the Scriptures promise one thing or the other. In some places we are told that the governments and powers are rather irrelevant. But God also addresses groups - cities, tribes, nations - as often as he addresses individuals, or more.