> Western nations came, they defeated their enemy, and they took their territory.

The various tribes also engaged in near constant warfare with each other, defeating them, taking their territory, and making the rest slaves. Cortez was only able to defeat the Aztecs because he was able to enlist the aid of the non-Aztec tribes, who hated the Aztecs because of the depredations of Aztecs against them.

The Inca empire was only recently formed before the Spanish arrived.

In North America, the Commanche carved out an empire in the south at the expense of the tribes that had been living there. See "Empire of the Summer Moon":

https://www.amazon.com/Empire-Summer-Moon-Comanches-Powerful...