Religion in the Middle Ages

[Iroscato]

Considering that era, I would say you would have seen more political/international wars in Europe.

...Your argument being?

It would have almost certainly caused a reduction in warfare. No crusades, for a start. No oppression of scientific discovery. No witch-hunts, less downtrodden women. Less likely to think diseases are simply punishments from God, leading to a better effort and understanding of their causes.
Basically take the scenario and fast forward to 2015, and we'd probably be a good 600-800 years more advanced socially and technologically.