A couple of quick notes and thoughts:
Dividing new states and/or reconfiguring them is constitutionally clear:
"New States may be admitted by the Congress into this Union; but no new States 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 4, section 3, clause 1.
The last part seems to mandate an approval of the both Houses of Congress.
Then there is the ambiguous exception of Texas is the exception. Under its term of admission, there is a clause that says that Texas may divide itself into up to 5 states. However, if it ever happened due to climate change in Hell, likely the Supreme Court would rule it invalid.
Currently, the biggest political danger we have in regards to our Federal structure is the rise of "rotten borough" states - not small states, but mini-states in terms of population. There are currently 6 states that are so small they have only one Congressional district (yet two Senators): Alaska, Delaware, North Dakota, South Dakota, Vermont, and Wyoming. While republicanism is a fine political system, vastly unequal representation leads invariably to corruption.