The royal rituals (that the common people are forced to participate in) definitely are consistent with the "supreme leader" thing. They're dictators on paper, and despite what you say, they're not dependent on popular support for their reigns. I'll give you that they're dependent on popular indifference for keeping the heads on their shoulders. If people hate them enough all those allegiance swearing would come to an end.

> I don't understand why any former colony would want to keep that.

Me neither, but Canada was specifically formed by people who wanted to keep that. Otherwise they would have just joined the USA at the start...