Answer:
The belief of Manifest Destiny played a major role in contributing to the Mexican-American War. This was the belief that the United States had a divine destiny to expand its territory across the continent, from the Atlantic Ocean to the Pacific Ocean. This belief was used to justify the expansion of the United States into Mexican territory. By claiming that it was God's will for the US to expand its borders, it helped to legitimize the US' actions and made it easier for people to support the war.