Mexico, Central and South America are extremely underrepresented compared to everywhere else, to the point where we made a thread with potential new maps and other content for those regions:
Asia also needs more content (and a rework of the current civs, if I had my way), but even they have more content than South America.
Nah, Japan needs more as well. The rework of the Meiji Restoration tech is really just about the Meiji Restoration tech. The rest of the civilization is still ass.