I don't think you can blame religion , which is a concept, but I do blame religious fanatics. These are the extremists that think everybody should think exactly like them.
Also, I think humans just like conflict. If everyone got along, we would be so bored. For example, why do people like reality TV so much? They like to watch people fight, nag, and be mean and nasty to eachother. A reality TV show that showed everyone getting along would surely not get good ratings. Have you heard that song "Heaven" by the Talking Heads? The lyrics go- "Heaven is a place where nothing ever happens".
If there was no religion it wouldn't make a blind bit of difference. Yes It's what causes most conflict but if it didn't exist something else would replace it.
No, there are too many conflicts in religion and money matters. The only way to harmonise would be to have a common cause ie a threat from say an alien species but that poses another war problem!