Cinco De Mayo - On May 5th, 1862, the French army was defeated by the Mexicans attempting to prevent the establishment of a French puppet state by Napoleon III, who would use the erstwhile Maximilian I of Mexico as his stooge. The unlikely victory by the Mexicans over the French at Puebla slowed the intervention, eventually forcing the end of the Second Mexican Empire. The victory at Puebla, however, may also have saved the United States - it was no secret that Napoleon III was eager to recognize the Confederacy, and a Mexican puppet state may very well have granted him the power to do so.
This TL explores the What if? scenario of a French victory at Puebla on May 5th, 1862, and the subsequent foreign support of the Confederacy, and the sustained power of Napoleon III's Second French Empire.