What does Article VI of the US Constitution declare is the Supreme Law of the Land?
Also, keep in mind the process of making amendments. Amendments take effect only when three fourths of the states say they take effect. The federal government does not decide or veto the making of amendments. So while the constitution is the supreme law of the land, its authority extends to the rights it grants to itself and which it prohibits the states from assuming. The founders were very, very wise.