Overview
This is a straightfoward and concise guide on how to succesfully invade and conquer the Americas.
Invasion
The Americas in Medieval II are very odd. They take ages to reach(around 8 turns which coresponds to 16 years!), units will glitch through Aztec pyramids, the Aztecs have the same voice over as the Nomadic factions, Aztec generals have no command yet a decent amount of dread and loyalty and are surprisingly easy to beat.
The rewards for taking these regions are huge. Although a far flung part of the map and somewhat strategically unimportant they offer vast opertunities such as very expensive resources, good training grounds for your generals and a great way to prctise your cavalry skills.
The first mistake you can make when invading is bringing infantry. Dont bring any, not even for siege battles, you will be able to recruit vast quantities of mercenraies and the Aztec infantry will just eat it’s way through almost all European infantry units.
Bring all cavlry in about 4 stacks. The best units in my experience are Knightly order units such as hospitaller, teutonic, templar and knights of santiago. Other units you should bring are chivalric/noble knights, lancers, gendarmes, gothic knights, imperial knights, portugese knights and if you have to then feudal knights. Dont bring mailed knights, demi lancers, conquistadors or broken lances because these have no armour on the horse and so will die faster despite high charge bonuses and attack.
Bring another stack of artillery to deal with smaller armies that you dont want to waste any casualties on.
TACTICS: These are simple. You need to deploy your cavalry in a single line as wide as it will go. when the battle starts move your troops forward, charge straight on into the enemies front with half your army and send the other half around the flanks to perform rear charges. With their generals having little to no command the Aztec units will rout fairly quickly especially when encountering scary things like horses and decent republican white folk who they done never seen before.
The Aztec bodyguard unit is a foot unit just like every other Aztec unit so direct your charge to hit the front-left corner of the unit and you will kill their general instantly no matter how much hitpoints he has.
Getting your troops into ambush positions is a great way to quickly wipe out your enemy, it gives you an oppertunity to attack from all sides instantly, doing huge damage within seconds of impact.
I cannot stress how important it is to outflank your enemy. The Aztec units are very light and are able to outrun tired cavalry units like gothic knights and generals bodyguard so cutting them off is the best way to run them down.
Do not leave your units in combat for too long because just like when fighting any other enemy in Medieval II your cavalry will start to take serious losses once in prolonged combat. Thankfully this game uses the old engine so you can actually cycle charge without taking huge disengagement losses.
No matter how tempting it is to use those late period infantry units like conquistadors, arquebusiers, aventeuer, heavy billmen or musketeers just dont because like i said earlier: the Aztec infantry can outrun all other infantry in the game bar peasants and can outfight most as well.
The Americas only have 6 regions. You should take out the Aztecs first just to get them over with and to have a bit of craic.