In the 1800s, the boundaries between the united states and mexico changed drastically because of
a. a revolution in america
b. changes in technology
c. a war between the two countries
d. the collapse of the mexican government

Option: C. a war between the two countries

Explanation:

In the 1800s, the boundaries between the United States and Mexico changed because they were in a constant fight with each other after America purchase Louisiana from France. The Louisiana Purchase led to the beginning of the westward expansion, allowed settlers to settle in the West. Texas became one of the places where American began to settle, which brought tension among the Spaniards living in Texas. The conflict arose between the two countries in the 1830s when Mexican President Antonio Lopez de Santa Anna tries to enforce laws and forced to signs a treaty in 1836 that led to the independence of Texas. The war began in 1846, came to be known as the Mexican-American War.