I'm not a scholar on Islamic history but for my TL I realize I need to know a lot more about it. I'm familiar with the Sunni-Shi'a "schism" if you want to call it that, and I realize it started off as more of a difference in political recognition of the line of Caliphs then real dogmatic differences (though I imagine there were some- and I know there are a lot more now).
What I wonder is- how "schism'd" can Islam get? It seems like Islam is far less fractured than Christianity is today, but that might just be because I don't live in a majority-Islamic society. Regardless, was there any point where we could see more fracturing of Islam? Perhaps either through liturgical differences (such as Nestorians v. Catholics and such), political differences or even socio-political differences- such as different branches of Islam in Malaysia and Somalia or some such (random country names don't hold me to them, just that kind of idea).