“it does not allow them to violate Article IV, Clause I”
That clause is specifically a mandate for the federal government, not the states, so it is impossible for the states to violate it.
Wrong again.
“In Luther v. Borden, 326 the Supreme Court established the doctrine that questions arising under this section are political, not judicial, in character and that ‘’it rests with Congress to decide what government is the established one in a State . . . as well as its republican character.’’
https://constitution.findlaw.com/article4/annotation18.html