George Washington could be killed say in the aftermath of Saratoga, and Horatio Gates looks like he could become the next Commander-in-Chief, but an act of cowardice costs him the position. Instead, Benedict Arnold, the Hero of Saratoga, could become the Commander-in-Chief. Benedict Arnold would have been a good general, and more important for the timeline, he was a power hungry guy. Arnold would have been a proper revolutionary military leader, refused to give up power, get the Army behind him, and overthrow Congress. The man would have been the founding father figure, the Liberator of America, so he might have gotten away with ruling by fiat. More likely you have a South American reaction to a power-hungry military dictator, Bolivar, and simply walk away from the United States. The same reason that the British couldn't control the United States by force will keep an American general from becoming Army-appointed Royalty, its too big.