I saw the video, but it seems to me that (naturally since this guy does genealogy charts mostly) he left out the reason why America could possibly even end up with a king. So he makes a tie to a royal family.
The thing is that the British Colonies were probably a bit less cohesive, politically speaking and less developed as British territories, than say our neighbors to the south.
The parallels however are uncanny and in the US, we never learn that the territory of the New Spain also had a Continental Army with a general who became the first ruler of the independent nation. I'm talking of course of General Agustín de Iturbide, roughly 30 years after George Washington. Both were commanders of their respective Continental armies, but while Washington became President of the United States, Iturbide became Emperor of Mexico. So it makes sense to compare both countries' antecedents to figure out why Washington could not possibly become a king.
If anyone is intesested in the subject, I'll be happy to expound in this thread. Otherwise, it's just a comment I'll make...