Answer:
When claiming statehood, the territories in the southwest gained through the war claimed lands on both sides of Missouri's border which caused unbalance between free and slaveholding states.
Explanation:
The Mexican-American War was the result of territorial disputes between Mexico and the United States after the annexation of Texas by the United States in 1845. Although Texas proclaimed its independence from Mexico back in 1836, the Mexican government consistently refused to recognize the independence of Texas, considering it as a rebellious territory. At the same time, the United States actively supported the Texans (immigrants from the United States) with both weapons and manpower, and all three Presidents of Texas, including rebel leader Sam Houston, were US citizens.
The annexation of Texas and the outbreak of war with Mexico caused a mixed reaction from American society. In the United States, the majority of Democrats supported the war, which was rejected by most of the Whigs. In Mexico, war was considered a matter of national pride.
The most important consequences of the war were the extensive territorial concessions of Mexico (about 55% of the national territory), as a result of which California and New Mexico - the lands of the modern states of California, New Mexico, Arizona, Nevada and Utah were given to the United States. American politicians spent several years intensely discussing slavery in the new territories, and finally decided on the Compromise of 1850 (only California was recognized as a state free from slavery), which replaced the Missouri Compromise.
