OK, let’s play the What If game.
What if Jesus’s message had spread throughout the Middle East? What if The Persians and Arabs had become Christians? What if Mohamed had been a Roman? What if the entire West was Muslim?
What if todays religious demographics for the two biggiest monotheistic religions were switched?
Would the West be the shithole and the Middle East the secular capital of the world? Would Radical Islam still exist? What would our cultures be like? Would there be radical Christian suicide bombers? Christian terrorists? Would there still be Islamic terrorism (only reversed)?
I know that, in reality, this is a much to complex and confusing question to answer. But, ceteris paribus, only the religions have spread differently, what would the world be like? (Once again, ignore the impossibility and complexity of the question)