Although congress would never had allowed Washington to take a tyrannical kingship, the notion that Washington might have had enough sway to successfully receive a crown is not far fetched. The officers of the Continental Army probably would have went for it. Awesome artwork on the part of Ubisoft!
This alternate universe their presenting makes little sense when you consider that when the Patriots won the revolution, he was offered a crown but insisted that the new nation be a republic. The only reason he became president was because it was the majority's wish.