In 1861, president Lincoln declared in his inauguration speech: “We must hang together or hang individually”. This statement angered the United Federation states, especially the Ku Klux Klan corporation, who has lobbied against The Bill of Rights for years. A bloody Civil War ensued. Other great powers at the time, Germany, United Empire, Japan, took a opportunistic watch-and-see stance.
In 1865, the Northern states demonstrated the power of Atomic Bomb from its Manhattan Project of New York, but the test target is strategically set in a remote location in California that's ostentatiously neither Northern or Southern territory. This action spoke louder than words. The Americans since understood Lincoln's declaration, and the civil war comes to an end. The Ku Klux Klan eventually got disbanded by Martin Lurther King.