Interesting that you mention this in the same post in which you lament the destruction of St. Nicholas Greek Orthodox Church. The Christian Roman empire, and certainly its Byzantine remnant, are a nice example of a political base for an authentically religious culture. Speaking of interpreting history through one's preoccupations, I wonder if you're aware of the late Stephen Runciman's view of the crusades as the last of the barbarian invasions.
In the West, of course, we have the unique polity that is the Holy See, which bids fair to remain influential for the forseeable future. Only today I started reading a diplomatic history of the Vatican in the age of the 20th century dictators. Small as it was, without this political base from which a religious culture works, history would have proceeded very differently.
Have you reached the part where the Japanese tried to sue for peace through the good offices of the Vatican and, in response, the United States dropped a nuclear bomb upon Nagasaki--the seat of Japanese Catholicism? Now that's what I call power.....