Final answer:
The Mexican-American War reignited the slavery debate and threatened the stability of the Missouri Compromise.
Step-by-step explanation:
The Mexican-American War affected the Missouri Compromise by reigniting the slavery debate and threatening the stability established by the compromise.
After the war, new territories were acquired, which raised questions about the expansion of slavery. The Wilmot Proviso, which proposed to ban slavery in these territories, sparked debate in Congress that lasted over four years.
The Compromise of 1850 was eventually passed to address the sectional tensions, but concerns about the response to the Fugitive Slave Law and the publication of Uncle Tom's Cabin further divided the North and South.