No, we are actually not homogenous at all. Even Arabs are pretty culturally divided, especially the Middle East vs. North Africa. We do have a sizable population though.

I would argue that the main barrier between Arabs and unity is authoritarianism.

Muslims are actually very diverse group. Not only Sunni / Shia rift which is major one but also differences between African/Middle Eastern/Asian Muslims. I think Indians and Chinese are much more culturally homogenous and more likely to take over world.

Islam is not a homogeneous culture. Totally different.