Question

What dynamics and issues allow Spain to conquer the Americas?

Answer 1

Spain took advantage of several things to crush native resistance. One was in taking advantage of native unrest to build alliances such as when Cortez had taken his 500 men to conquer the Aztec Empire...with the help of the empire's enemies. Everyone remembers the small number of men that he took with him to bring down such a powerful enemy, but what is sometimes overlooked is that they didn't do it alone. The Spanish were keen to make friends when it benefited them in the New World.

Another factor was technology. Gunpowder, muskets, cannon, horses, metal armor...all of this was unknown to the natives of the New World until the Europeans brought them over. When the natives were still using spears, bows, obsidian knives, and wooden dress as protection, all of that paled to the power of a lead ball shot from a musket from a hundred yards away.

But one factor that no one expected was the introduction of diseases that the New World natives had never been exposed to before. Over the course of a century or so, smallpox and other diseases destroyed the native population much more completely than what the Spanish could ever do with their advanced weapons. They simply had no resistances to these and many other diseases.

Answer 2

@Captain_Page_Turner gave a good answer. Basically they would just ambush the different cities. The spanish had better weapons so they made it possible to do so, and plus bring crazy fear among the tribes.