What did the Spanish bring to the Americas that contributed to the destruction of the early civilizations?

Answer 1

The Spanish brought new diseases to the Aztecs. With no natural immunity to the new diseases of the Europeans, many of them fell sick and died.

European diseases smallpox, influenza, measles and typhus were brought by the Spaniards and spread to the early civilizations. Additionally, in terms of technology, the Spaniards had rifles, horses, forged-iron weapons, canons, and numerous other steel-based technologies against which stood Native infantry with wooden weapons.