Religion is prior to civilization. That is, civilization is the by-product of religion, not its cause.
I guess that explains the Dark Ages, the Inquisition and the two bloodiest wars the human race has ever indulged itself in, all in the same place.
Without France, there probably wouldn't have been an America. Most likely wouldn't, actually.
You are viewing history in narrow slices. No one has seen the long-term. Christianity has itself changed, mutated, spliced and spawned into various new religions- much like every other man-made systems of superstition.