Mayincatec is The Theme Park Version or Hollywood History version of Central and South American Indians. Basically, the Mayan, Incan and Aztec cultures are blended together, and then sprinkled with elements from other native cultures, and whatever nonsense the authors dreamed up - most likely because they Did Not Do The Research. It's a bit like Ninja Pirate Zombie Robot.
The look and feel of Mayincatec:
The following list is cribbed straight from the TV Tropes Wiki, and it does a great job of summing up the Mayincatec, as presented in film.
- Human Sacrifice: cutting out the heart of a living victim atop a ziggurat (step-sided pyramid).
- Lots of priests, religion and monstrous gods.
- Big stone temples with distinctive stonework, usually equipped with traps and underground labyrinths.
- Feathered headdresses, clubs studded with chunks of obsidian, loincloths.
- Corn harvests, sun worship.
- Complex stone jewelry: earrings, necklaces, chest pads.
- Ornate and colourful decorations, geometric patterns. Intricate and scary carvings.
- Jungle settings and an abundance of wildlife: snakes, spiders, jaguar and monkeys.
- A drug culture — coca and hallucinogens.
- Conquistadors often feature as conquerors of the Mayincatec.
- Desiccated bodies in ceremonial outfits: unwrapped mummies.
- Gold and hidden treasure. Idols. Cursed artifacts.
- Sometimes hidden advanced technology and/or links to Ancient Astronauts.
- Giant line drawings out in the desert, like the Nazca Lines.
- The Mesoamerican Long Count Calendar, which is set to run out of days December 20, 2012.
- Sometimes, when the producers do the research, an extremely sophisticated grasp of astronomy.
- If they use a specific god, it'll most likely be Quetzalcoatl, the Plumed Serpent. Since they'll probably know nothing beyond his name, they'll likely show human sacrifice to him, although he was perhaps the only god in many pantheons who didn't ask for it. 
- Beat Still My Beating Heart
- Gods Need Prayer Badly
- Human Sacrifice
- The Power Of Blood
- Religion of Evil
- Religion Is Magic
Game and Story Use
- In reality, the Aztec, Inca and Maya cultures are very distinct, and worth researching individually if your game is going to spend any time among any of them.
- Of course, if your campaign is a globe-hopping Pulp adventure, with only one or two sessions spent amongst (mostly running from) the natives, you may be able to get away with just a brief surface-level impression of them. If you're not going to do the research, though, you might consider making up your own culture (or maybe even calling them Mayincatec) just so players know up front that you aren't worried about being historically or culturally accurate.