Anyone who thinks mesoamerica should be a cakewalk and weren't that advanced needs to not be a dumbfuck and read Bernal Diaz's "Conquest of New Spain" and Hernan Cortes' letters back to the Emperor. Europeans didn't beat the Aztecs, they just exploited the situation of a loosely constructed government, and that isn't modeled in the game. This is in stark contrast to better forms of governance in North America with the Iroqouis Confederacy being the prime example, which led to resistance to expansion well into the 1800s. Sure, Aztecs didn't have guns, horses, etc., but most of the time the Spaniard's horses were bogged down or ineffective, especially during any siege, and they were constantly low on powder for their rifles. They lost over 2,000 men getting expelled from Tenochitlan the first time and Cortes was almost killed, pretty handily in fact. Their two handed obsidian blades were better made than much of what the common soldiers were using, they just didn't have pikes(they later fashioned some out of captured Spanish steel), and obsidian is obviously not as durable.
Don't even know why I'm responding. Read a fucking history book, and Paradox should too. No excuses after four iterations of their "world spanning" strategy game.