The most accurate response regarding how the Mexican-American War led to greater sectionalism within the United States government is:
C There was great tension between pro-slavery and anti-slavery representatives over how new territories won would handle the issue of slavery.
The war resulted in significant territorial gains for the United States, particularly from the Treaty of Guadalupe Hidalgo in 1848, which raised critical questions about the extension of slavery into those newly acquired territories. This debate intensified sectional rivalries, as the North and South had starkly different views on the expansion of slavery, leading to increased conflict in Congress and contributing to the tensions that would eventually lead to the Civil War.