Was the Mexican-American War an "unjust land grab" or "good foreign policy?" I think it was inevitable with Manifest Destiny and westward expansion. So I have always liked President Polk and we gained so much from Treaty of Guadalupe Hidalgo 1848.
Did we gain the Civil War from our invasion of Mexico?
No. But we did get the territory that would become California, Nevada, Utah, New Mexico, and Arizona. Civil War could have been avoided.
"The
Wilmot Proviso, one of the
major events leading to the
American Civil War, would have banned
slavery in any territory to be acquired from
Mexico in the
Mexican War or in the future, including the area later known as the
Mexican Cession, but which some proponents construed to also include the disputed lands in south Texas and New Mexico east of the Rio Grande."
King Cotton had the same stranglehold on US economics and politics in 1848 as oil has on global affairs today. Wilmot's proposal split the Democrats of his day into northern and southern wings and paved the way to Civil War.
Wilmot Proviso - Wikipedia the free encyclopedia
But the West was not suitable to grow Cotton. Popular sovereignty is in the Constitution in the Preamble, Article VII, and in fact was also in the Declaration of Independence. Cass came up with nothing new. At some point we were going westward. At some point the territorial issue had to be resolved. Lincoln had made his mind up for war back in 1858 when he ran and lost for US Senate in Illinois.
"A house divided against itself cannot stand." I believe this government cannot endure, permanently, half slave and half free. I do not expect the Union to be dissolved; I do not expect the house to fall; but I do expect it will cease to be divided. It will become all one thing, or all the other. Either the opponents of slavery will arrest the further spread of it and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction, or its advocates will push it forward till it shall become alike lawful in all the states, old as well as new, North as well as South.