Answer:
The President of the U.S.A was James K. Polk
Step-by-step explanation:
The Mexican-American War (1846-1848) was the first armed conflict in the United States, which occurred primarily on foreign soil. It pitted a politically divided and militarily unprepared Mexico against the US administration's expansionist-minded approach. James K. Polk – President, who claimed the United States had a "manifest destiny" to extend across the globe to the Pacific Ocean. The fighting began with a border skirmish along the Rio Grande, followed by a series of US victories.