It is pretty obvious the two coasts want to go their own way. Let them.
The two coasts would call this unfair. US in the middle of the continent, undivided. THEM in two divided portions with no joining border between them. They would complain US took in more land and made ourselves larger than them.
OTOH, they just might agree to this. US would find we had two fronts to navigate: east and west. In the right frame of mind, this might be the solution to their advantage. It would be a plus for them. US, not so much unless we had eyes in the back of our head or to be more eact, we had 4 eyes. Canada, Mexico, East Coast, West Coast.