Why did President Polk declare war on Mexico?

Polk's request to declare war on Mexico in a dispute over Texas. Under the threat of war, the United States had refrained from annexing Texas after the latter won independence from Mexico in 1836.

Explanation:

On May 13, 1846, the U.S. Congress overwhelmingly votes in favor of President James K. Polk's request to declare war on Mexico in a dispute over Texas. Under the threat of war, the United States had refrained from annexing Texas after the latter won independence from Mexico in 1836.

Explanation:

the us constitution is a living document, meaning that it can be changed over time as the country changes.