If you create a new state from uniting two other states, then that removes one state from the Union and requires Congressional approval. Removing a state through secession should be no different.
Please note, my comment indicated the "monach" was elected, not hereditary titled.
But still a title of nobility and therefore covered by the Constitution. Titles don't have to be hereditary, the U.K. grants individuals titles of nobility which are not passed on to the next generation, Margaret Thatcher is an example of that.
Why? It's not enumerated. The powers not delegated ....
But still a title of nobility and therefore covered by the Constitution.
The Constitution states, 'No Title of Nobility shall be granted by the United States'. Hamilton advocated election (requirement for republican government) of the executive for life. Call him a monarch, Mr. Peanut or anything you want, you must call him something. But titles of nobility are for an 'order of men in several countries to whom privileges are granted at the expense of the rest of the people' [Bouvier Law Dictionary, Rev. 6th ed. (1856)]. Madison argued against tiles not 'because I fear the danger of any power they could confer, ... instead of encreasing they diminish the true dignity and importance of a republic, and would in particular, on this occasion, diminish the true dignity of the first magistrate himself.'