Harry Turtledove's book "Through Darkest Europe" has, in my opinion, a very unrealistic pod. In the novel, the Islamic world is very liberal and democratic and Europe is a hotbed for Christian fundamentalism and terrorism. The issue is not the events themselves but the pod that led to them. The Pod is simply that Aquinas says that faith should trump reason, and Al-Ghazali thinks that the two can work together. I think that it can be generally agreed that this hyperbolic. However the situation is still very interesting, so try to create this same switcheroo but with a more realistic set of events leading to it.