U.S. v. U.S. | CIVIL WAR (1861-1865)
Seen by abolitionists as a means to spread slavery, the Mexican-American War vaulted the issue up national debate charts and trained an entire generation in warfare. Finally, upon Abraham Lincoln’s election to the presidency, seven Southern states seceded and four more eventually followed out of a fierce dedication to states’ rights. Just kidding, they wanted to own black people.
The resulting conflict claimed a million casualties and bankrupted the South for the next century. When one party wants out and wins, it’s a revolution! When that party loses, it’s a civil war (sad trombone).