How did gaining land from the Mexican American War cause sectional differences (Sectionalism) to increase between slave states and northern states in the United States?

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Gaining land from the Mexican American War caused sectional differences (Sectionalism) to increase between slave states and northern states in the United States in that "There was great tension between pro-slavery and anti-slavery representatives over how new territories won would handle the issue of slavery."

These territories gained from the Mexican-American War after the signing of the Treaty of Guadalupe-Hidalgo accelerated the already existing conflicts between the northern states and the southern states.

For instance, the admission of California as a non-slavery state represented a major problem for the governments of the southern states in that they believed this affected their control over slaves.

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