Article. IV is about the states, and their relations to each other and top the national government.

Section. 1.

Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.

Section. 2.

The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.

A Person charged in any State with Treason, Felony, or other Crime, who shall flee from Justice, and be found in another State, shall on Demand of the executive Authority of the State from which he fled, be delivered up, to be removed to the State having Jurisdiction of the Crime.

No Person held to Service or Labour in one State, under the Laws thereof, escaping into another, shall, in Consequence of any Law or Regulation therein, be discharged from such Service or Labour, but shall be delivered up on Claim of the Party to whom such Service or Labour may be due.

Section. 3.

New States may be admitted by the Congress into this Union; but no new State shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States, or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress.

The Congress shall have Power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States; and nothing in this Constitution shall be so construed as to Prejudice any Claims of the United States, or of any particular State.

Section. 4.

The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened), against domestic Violence.

I read this in 1:54.

Article IV is about the relations of the states to each other and to the national government. The provisions assert a soft superiority of the national government over the states. This becomes much clearer in the 14th amendment (1865) but is already clear in the words, “The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.”

The first thing that jumps out to me is this bit from Section 3:

no new State shall be formed . . . within any other State . . . without the Consent of the Legislatures of the States concerned.

That happened when West Virginia was split from Virginia in 1863. Western Virginians were loyal to the Union and not interested in fighting for slavery. They were closer to Pennsylvanians and Ohioans (with whom the shared the Ohio River) than to the slave-holders over the mountains away East.

So they created a separate state government from the secessionist one in Richmond, and they claimed that theirs represented the state. It was they who provided the consent required by the constitution for the formation of the new states out of the territory of an old one. President Lincoln, who was a staunch believer in the constitution and admirer of the founders, held his nose and approved the new state of West Virginia.