Mississippi

The Aztecs were not just a tribe of Indians in Mexico when Columbus landed; they were an empire.

 As an empire they conquered other tribes, sent out expeditions of exploration and conquest.

Perhaps they sent out expeditions in small boats along the coast to the Mississippi region and fought against Mississippi mound builders.  

That way you can use your Imex and Revell Indian sets, sans the men armed with rifles and the horse with riders, as a new opponent of the Axtecs.

The the Thunderbird can fight the Quetzalcoatlus!

On Red Bubble you can get official Bunker Talk gear:
 https://www.redbubble.com/people/bunkertalkwar/works/30633204-world-war-two-era-us-army-lee-tank-with-soldiers?asc=u

Quetzalcoatl

Science used to tell us that dinosaurs and related reptiles had a smooth leathers skin.  The science was settled.

Then science told us that some dinosaurs and similar reptiles had feathers.  Once again the science was settled.

Anthropologists told us the Aztecs told us that they were in contact with Quetzalcoatl, a flying feathered serpent.

 Paleontologist tell us that men and dinosaurs never lived together.  The science was settled.

  Quetzalcoatlus, the feathered serpent flying reptile did exist say Paleontologists.  But how did the Aztecs know this if they did not see them?