We have no choice but to add US states in 2021!

[Statistical]

4. Yes states can be formed by splitting existing states but it requires support of the state.

Yes states can be formed by splitting existing states and states can also merge to form a new state. You can even carve territory off two or more states to form a new states. However in all those scenarios it requires support of Congress and the state(s).

There is a lot of cultural and regional identity in states. Even though it provides political power not sure how likely the people of Texas would go for splitting Texas in half. I mean technically yes it can be done just not sure how viable it is.

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.

Article IV Section 3 US Constitution