John Adams wanted to give the President a style, but he thought “Your Excellency” (despite G. Washington being called that both before and during his Presidency) was too weak, given that many state Governors had that style, as did foreign ambassadors.
He favored “His Highness the President of the United States of America and Protector of their Liberties.”
Some suggested or joked about “His Elected Highness” or “Elected Majesty” or “His High Mightiness”.
Most nations now style their President “excellency” and the US President is refereed as such in international diplomatic protocol.