http://www.bigredhair.com/books/aztec-empire/episode-one/
Furthermore, in the notes, it states
The population of the entire mpire is widely accepted as being around 20 million. Sheburne Cook and Woodrow Borah, leading researchs of Mexican population history, convincingly argue in Conquest and Population: A demographic Approach to mexican History, that there were 25.2 million people in Mexico when Cortes arrived iin 1519
I've always heard the empire's population as 5 million. 20 million would make it larger then any nation in europe at the time, (unless my numbers for those are off too), much larger then ones of comparable area; and is hard to believe, even as somebody who constantly talks about how cool Mesoamerican accomplishments are. At the same time, I've always heard 25 million is around the range of where the total population of Mexico (though I suspect "Mexico" here means "Mesoamericia" rather then moodern mexican borders, so not including very north mexico, and including some of guatamala, belize, etc) was at the time, the Aztec empire only having 20% of that, despite covering, what, 40% of mexico seems off to me. But if it is 20 million, then that would mean the Purepecha empire, despite being extremely large as well, had a disproportionately little amount of people.
Neither the 5 million or 20 million figure seems to make much sense here.
(Also, small bonus question; The notes also identify the infamous Snake labret with the articulated tounge as being Mixte created: I've always thought it was Aztec, which is it?)
France (the most populated country in Europe at the time) had around 18-20 million people by that time so its not THAT huge of a difference (makes sense both are regions with lots of readily available arable land and fresh water, except Mesoamerica is larger), and Mesoamerica tends to have seizable populations, 600 years before them the Mayan regions should have sustained similar populations, according to new findings: https://actualidad.rt.com/actualidad/262932-descubren-60000-estructuras-mayas-guatemala
I think 25 is definitelly on the large side of the scale, but the Triple Alliance's population is often compared to that of France in most demographic studies I've seen (Im not a historian), the first days of the colony of New Spain talk about nahuatl populations well into the 12-18 million inhabitants at the very least in the Valley of Mexico, and to give you a gruesome example, the first large smallpox plague is calculated to have taken somewhere in the vicinity of 8 million people in the Valley of Mexico region, give or take a million.
Large empires like the Tarascan (Purepechas) Empire to the north should have had similar populations to that of the Triple Alliance (not THAT big exactly, but big enough that they were able to directly compete with the Triple Alliance on equal footing both militarily and economically), and other older cities like the kingdom of Colima also had considerably large polities (not 25 million large, but considering the capital was 125,000-ish a couple of millions sounds reasonable), the Mixtecs and Zapotecs in Oaxaca should have also had no small ammount of residents as they defeated the early Aztec Empire even when Moctezuma I mobilized almost the entirety of Tenochtitlan, enough to make it look like "a deserted place" according to Tezozomoc.
Hmmm, let me give a concrete example of the size of the individual polities we are talking about, as your comic points out, Mexico-Tenochtitlan was a city of around 200,000-ish people (some author go as high as 500,000, but lets stick with low end-numbers), now bear in mind Mexico-Tenochtitlan WASNT the largest city in the Valley of Mexico, Cholula and Texcoco were suposedely larger, in fact the war that led to Mexican acendacy was the war with Azcapotzalco, now, Azpotzalco means "Anthill", it was a city, so big, so populated in comparison with Mexico-Tenochtitlan that it was called "Anthill" because it "had so many people that it looked like a human anthill".
Also, this is very nitpicky of me, but why are the Mayans and Mexicans in the comic dressed like they are preparing to film a porno? And why are the "mayan warriors" dressed like stereotipical african cannibals? And they wouldn't have used arrows, those were used for hunting and sport, the ranged weapon of preference was the Atl-Atl.
Cortez's recount of the conquest makes it very clear that both mayans and nahuatl forces wore cotton-based armor, VERY good cotton armor, good enough that one of his problems early one was keeping discipline after the battle, his soldiers would routinelly try to kill each other at first for pocession of their armors, which were more resistant, more lavish and (obviously) more adapted to the environment than their own.