I certainly wouldn't advocate a monarchy for the United States, because the US has also come up with a system that works well. That's the most important thing for any nation.
The question has been asked: So you think that a monarchy can be superior to the Constitution of the United States.
The problem is, in my country, the monarchy would not be replaced by anything like the Constitution of the United States. It's not likely to be in most monarchy's. America wound up with a wonderful constitution out of revolution - that's not really all that common.
So does being in the Commonwealth alone make you a monarchy, or is it some extra decree?