Shoot I’m not from Minnesota :/
The correct answer is - The Spanish established their language when they colonized the territories.
During the period of the great discoveries the Spanish managed to occupy most of what is now South America. They implemented their language, culture, and laws, very often with using force and violence because lots of the native people were not willing to give up on their own culture, language, and way of life. The Spanish managed to prevail, and ruled for long enough that the Spanish language becomes the dominant language in nine South American countries.
Westward expansion meant that the US acquired ever increasing amounts of land, and needed people, farmers, to settle there so it could maintained without a huge military presence