I'm finding alt-history a bit more challenging than I expected. The story in question is a bit tricky, and I'm having difficulty with motive. You can't just make changes willy-nilly. There has to be a reason. If I decide to explore what might have happened if, say, Kublai Khan had not been recalled to Mongolia and instead participated in the Crusades as he promised, then I have to understand both what really happened and come up with a plausible reason why it happened differently.
That isn't what I'm writing, though it might make a very interesting and possibly risky novel.
I'm finding this sub-genre is full of a different kind of challenge than most of my writing, with a new set of problems. Currently I'm about 350 words into the story. It's not much, I know, but it's better than none.