Incas were not writing at this point. They had a knot system.

To remind people who are what, Aztecs (Mexico now) were North American in today's term, Maya were also North American, bordering Central America (Yucatán peninsula in Mexico) and the Incas were all the way down in South America in Peru.

Meso American is a weird term that does describe the Aztecs and Mayan people... Historically. But, not the Incas and it doesn't really give you the full picture of what we consider to be located where today--which makes people confused about the differences between the three.

Another quick distinction is that Peru has some extremely old cultures that most likely are the far past ancestral peoples of the Incas (with some cultures being a whopping 5000 years old at Caral), but the Incan Empire itself at its height only lasted about a century before being met with the Spaniards and disease.

Kinda same goes for the Aztecs whose ancestral people were influenced by the ancient Mayans (whose archaic age was 4000 yrs ago), though Mayans themselves also stuck around. Anyway, the Aztecs at their height only lasted about a century as well before the Spaniards and disease.

Mayans were really the older culture out of the three that at least seems to exist as a singular cultural entity between the Incas and Aztecs in archaeological records, their cities seem to have been around for millennia. But unlike the Aztecs, the Mayans had their heyday in the past and were a shadow of their former self in comparison to the newly invigorated and growing Aztec and Incan neighbours.