Answer:
propaganda spread by the Spanish.
Step-by-step explanation:
The Spanish often painted Mexican people with negative light, They came to Mexico with the intention to colonize the territory, but quickly referred to the Mexican locals as "Violent" the moment they put up a fight. On top of that, simply because there's a difference in their culture, Spaniards created the stereotype that Mexicans are "superstitious", "thieving" , and "lazy"
This stereotype was spread across the American borders. Since many Americans weren't really familiar with Mexican people, many of them took the words of Spaniards without actually making their own judgement. Raymundo Paredes beloved that This created a lot of Anti-Mexican Sentiments in United States.