OK - here goes.
POD 1863 - Gettysburg goes better for the Union.
Gettyburg goes better for the Union. Pickett's charge is even more of a disaster than in OTL. Lee, overcome with the magnitide of the disaster gallops forth on Traveller to rally the troops, and is killed by a Union sharpshooter. Meade, smelling blood in the water attacks, and manages to bag most of the Army of Northern Virginia. Scattered remanents flee to Virginia. With stories of Vicksburg and Gettysburg abounding, Confederate morale crumbles.
By late August, Richmond has fallen, and the Confederacy is in pieces. Only the Confederate Army of the Tennessee is still intact, and it is defeated in September. The Union declares an end to combat operations by the end of October.
However, several large Confederate formations, still full of fight, flee to Mexico. They offer their services to the Emperor Maximillian (and the French) who take them up on it. Benito Juarez is killed, and his movement suppressed. Lincoln and the North choose to ignore this for now - reconstruction is the name of the game.
From 1864 - 1874, there are a series of raids across the border by the ex-Confederates, who by that time are little more than well-organized bandits. In 1874, one of these raids penetrates to Austin. There, the state governor and several legislators are hanged for 'Crimes against the Confederacy', and several African Americans are lynched.
The raid enrages the people of Texas, as well as the Federal Government. An ultimatum is presented to Maximillian by President Hancock - allow the US the follow up on its investigation or face war. Maximillian, realizing that the French will not back him against the US, accedes to the demands of the US.
However, word of the ultimatum gets out, and, correctly fearing they would be prosecuted, the ex-Confederates stage a coup, putting Nathan Bedford Forrest on the throne as the Emperor of Mexico. The US sends a huge army under Sherman and his Cavalry leader George Custer to depose Forrest.
After several months of regular warfare (which sees all cities in Mexico fall to the US), and several years of brutal irregular warfare, Forrest and the Confederates are defeated. Some in the US call for annexation, and some call to simply leave. The US decides on a compromise. Not wanting Mexico for itself, and not wanting another power to dominate the devastated country (which has lost 25% of its population to most disaese and famine caused by infrastructure destruction), the US makes Mexico an 'Unicorporated Territory'. The US military occupies the country, and a US Viceroy (Officially called the Provisional Resident Leader). US business interests dominate the country. There is a nomimal Mexican government, and some law enforcement control (over Mexicans, not USAians), but no real power.
By 1914, there are rumblings of real independence as Europe decends into chaos...
Mike Turcotte