So after some long thinking, I believe I have figured out what Anahuac is going to be, and it's mostly going to be an area of necessity.
In all honesty, I don't have the time or energy to fully flesh out every Native American nation, and this project is long overdue as it is. However, I'm going to try my best to do where Warhammer kind of skimped out.
The nations of Anahuac are, as stands:
Dinetah: My North America/Naggaroth. While the siabra do dwell here, they don't control nearly all of the continent. Much of it is still inhabited by native Anahuacans, but they are often either in hiding or fighting losing battles. The siabra so far haven't expanded past the Grandfather River (Mississippi-expy) in a nod to post-revolutionary America, and much of that remains wild though the siabra inch ever closer.
Aztlan: My South America/Lustria, this one is pretty close to the Warhammer source material. The aztlan are going to be a bit more explicitly alien and not outright hostile to humanity, but very few people want to venture into the jungles regardless. Like Dinetah there will be native tribes, but they tend to have a more neutral relationship with the lizardfolk rather than the hostile relationship Dinetahns have.
The Wracked Sea: My Caribbean analogue, this one is a bit new to the setting. This is not only going to feature pirates and Europan colonials, but also my version of the Vortex - making the Wracked Sea a convenient place to have Pirates of the Caribbean-type pseudo-fantasy adventures. Undead pirate crews, voodoo cults, etc.
At least until I change my mind, that's how Anahuac stands at the moment. By far the 'smallest' of the continents, but the vast stretch of it is supposed to be unexplored and mysterious to easterners who are journeying west for fame or fortune. These areas are gonna come about heavily in the descriptions, but I think they'll work out well
Next time is the last stop on the tour, which are regions that don't really fit into a single continent, but it should be a pretty small entry.