How can we get the American Republic to fail, and instead of fracturing into a group of individual countries, the United States instead becomes a monarchy?
I've thought something along the lines of Madison and Hamilton cooperating on a plan for the future of the American nation, that results in the country becoming a constitutional monarchy, perhaps heavily influenced by the British system.
If we assume George Washington turns down the role of King of America, who would locially be the next choice? Would they turn to a brother of a European monarch? Perhaps someone like Augustus Ferdinand of Prussia? {Just off the top of my head}