Final answer:
The United States changed as a result of the war with Mexico through territorial expansion, heightened debates over slavery, and increased military experience.
Step-by-step explanation:
The United States underwent several changes as a result of the war with Mexico. One significant change was the acquisition of a large territory, including present-day California, Nevada, Utah, Arizona, and parts of Colorado and New Mexico. This expansion of territory greatly increased the size of the United States.
Another change was the intensification of sectional tensions over the issue of slavery. The acquisition of new territory raised debates and conflicts regarding whether slavery should be allowed in these regions.
Lastly, the war with Mexico led to increased military experience and confidence for some American officers who would later play crucial roles in the Civil War, such as Robert E. Lee and Ulysses S. Grant.
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