Answer:
The act of the U.S.A in going to war with Mexico proved advantageous in terms of allowing the nation to continue its territorial expansion as it was envisioned by President Polk. It also proved the strength of the U.S. in terms of "patriotism."
On the contrary, the act of the U.S.A. in going to war with Mexico cost the country a lot of money and loss of many lives. It also worsened the issue about "slavery."
Step-by-step explanation:
The "Mexican-American War" occurred from 1846 to 1848. The war started because of the annexation of Texas.
The U.S. believed that annexing Texas would allow them to expand their territories, however, the Mexican government did not recognize such event. They even prevented diplomatic relationship with the Americans when the Americans attempted to settle the issue with them.