“A secession would not be polite and non-violent.”
Also involved is the large amount of “Federal” property that would be on the wrong side of the border, no matter where you draw the line. Then there is debt- one side would be left holding the already unpayable bag.
The decision to involve the military would be strongly influenced by this enormous pile of money, debt, responsibility, and real estate.
Norway seceded peacefully from Sweden. However, that is not likely in our case.