What kinds of features should I put in a fantasy Latin America?

I've been thinking about reviving an old project of mine that involves worldbuilding an alternate history in which the Aztec Empire survived European colonization, and at some point it had a revolution inspired by the Mexican Revolution and became a socialist state. So it's basically an alt-Mexico that kept the indigenous culture of Mexico but incorporated some of the institutions from socialism.<br><br>This needs extensive worldbuilding, especially the geography, since for the Aztecs to have survived the colonization attempt the geography of this world should be such that colonization was much more difficult.<br><br>So it's mostly going to be based on Mexico, but Latin America is diverse, and I believe the full continent has a lot to offer in terms of geography and biodiversity. I think it's fair to say that I'd be relying more on the Americas for inspiration, and not including European and African influences, (with maybe the exception of the Caribbean, and the border with the United States, which in this world would be an entirely different country) but I want to make sure I'm not missing anything. Is there anything good from South America that I should consider when designing my alt-world's geography and biodiversity, and its subsequent repercussions for climate and weather?<br><br>I want to keep the continent's width similar to ours, but I wonder if it would be interesting for the sea connecting the Caribbean to the Pacific to take over the entire Yucatan Peninsula. I suppose that would create a lot of trade and travel challenges, but it would also create a lot of coast, which would allow the Aztecs to have a large navy, and perhaps even a marine culture. Or maybe that's too much and I should keep the Yucatan but make it a swampy, marshland area, in which case I'd imagine it difficult for the conquistadors to navigate through.<br><br>An idea that came to mind is that perhaps other pre-Columbian civilizations could also have survived their colonization attempts if the geography was different, however, maybe it's better if it was mostly the Aztecs. I don't know, which one would you think is more interesting?