If the West coast, New England and the blue midwestern states all created a country with Canada (let’s be honest Canada would likely merge with them, not them joining Canada) it would still be the most powerful country in the world. Leaving the Great Plains and the South as their own country. States that I imagine would follow this hypothetical would be; Washington, Oregon, California, Nevada, Arizona (maybe), New Mexico, Colorado, Minnesota, Illinois, Michigan, Pennsylvania, Virginia, Maryland, Delaware, New Jersey, New York, Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire, Maine. Hawaii would probably go it’s own way but maintain military ties with this new country. Alaska could join because it would make the most economic sense for them. That would leave Texas and Florida as the big dogs of the new country. Would still be a strong country but not nearly as strong as the new one. Both would be nuclear powers so there likely wouldn’t be a war between them. Could still maintain military and economic ties of some sort. Maybe have a mutual defense treaty similar to NATO.
I imagine after some time, maybe 20-25 years, there would be a form of reconciliation between the two countries and the creation of a new country would happen.