Final answer:
The Mexican War was caused by the belief in Manifest Destiny, which fueled American expansionism and led to conflicts with Mexico.
Step-by-step explanation:
The cause of the Mexican War was Manifest Destiny. Manifest Destiny was the belief that it was the destiny of the United States to expand its territory from coast to coast. This belief fueled American expansionism and led to conflicts with neighboring countries. The Mexican War was a result of the territorial ambitions of the United States and their desire to acquire land from Mexico.
Learn more about Manifest Destiny and the Mexican War