Answer:
The Spanish were able to defeat the Native Americans so easily, as they were able to leverage multiple advantages, including:
1) Creating alliances with other native tribes that were at war with the one the Spanish was trying to topple.
2) Making use of superior weaponry and defenses, including but not limited to the usage of muskets, cannons, iron armor, etc.
3) Bringing European diseases that were more harmful to the Native Populations then to themselves.
etc.
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