Pope Pius IX supported the Confederacy in the Civil War. He was the only head of state to refer to Jefferson Davis as the president of a country and he recognized the Confederacy as a nation. Robert E. Lee refered to the Vatican as the South's only friend. When Davis was in prison, the pope sent an autographed picture of himself and had nuns ask for his release.
The pope's interactions with the rebels pissed off Lincoln. Because the pope controled a country at the time, what would have happened if the United States declared war on the Papal States?