[4CJ]

And the Constitution EXPLICITLY states the Constitution will be the supreme law of the land, "...any Thing in the Constitution or Laws of any State to the Contrary notwithstanding."

Of course. And it applies to those states that are members of the Union, not those that have seceded (no prohibition against it!)

The later states were admitted under the provisions outlined in the Constitution, which was adopted by the original 13 states when they ratified it.

But the original states did not need congressional approval to be admitted. SCOTUS has ruled the states equal (despite the latter states admission having to be approved by Congress). There still is no requirement for ANY state to seek permission to leave.

[4CJ]

If nine states had the right to secede from the Articles of Confederation despite the legal requirement that all 13 must agree, then the states seceding from the Articles retained the right to secede from the Constitution.