Article I, Section 9, Clause 8: No Title of Nobility shall be granted by the United States [emphasis added]: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State.
Article I, Section 10, Clause 1: No State shall enter into any Treaty, Alliance, or Confederation; grant Letters of Marque and Reprisal; coin Money; emit Bills of Credit; make any Thing but gold and silver Coin a Tender in Payment of Debts; pass any Bill of Attainder, ex post facto Law, or Law impairing the Obligation of Contracts, or grant any Title of Nobility [emphases added].
They do it all the time they just call it something else. We like Royalty here whether we recognize it or not. Well not thee and thou of course.