Cultures where marriage is predominantly a governmental matter rather than a religious one are all, as far as I am aware, heavily influenced by the cultures of western Europe.
My understanding of non-Christian cultures is that this claim is dubious. Of course the notion of a separation of religion and state is itself a modern western notion, so it's hard to say what this means for most cultures.
Suppose I told you that I knew for a fact that the following statements were true:
You’d think I was crazy, right?
Now suppose it were the year 1901, and you had to choose between believing those statements I have just offered, and believing statements like the following:
Based on a comment of Robin Hanson’s: “I wonder if one could describe in enough detail a fictional story of an alternative reality, a reality that our ancestors could not distinguish from the truth, in order to make it very clear how surprising the truth turned out to be.”1
1Source: http://lesswrong.com/lw/j0/making_history_available/ewg.