Answer:
The Notherners were interested in stopping the expansion of slaves states after the war ended, since the Mexican-American War resulted in the annexation of Texas to the United States, as a slave state, something that changed the balance between free state and slave states in favor of the latter.
Southerners were interested in the opposite, after the annexation of Texas, they wanted to continue expanding slavery to the Western United States, something that the Northerners opposed. In the end, this would be the main spark that ignited the American Civil War just a decade later.
