Look at the reverse: can the U.S. amend the constitution to say, "The U.S. is made up of the fifty states, plus Mexico"? Certainly Mexico would hold a minority

Look at the reverse: can the U.S. amend the constitution to say, "The U.S. is made up of the fifty states, plus Mexico"? Certainly Mexico would hold a minority vote and not be able to influence the outcome. Does that mean that all the people of Mexico are "ignoring the constitution" if they don't want to be in the United States?