I don't think we'll completely lose the country as a unique entity - there will always be those who live and die by the Constitution and the Founders' vision - but you can damned sure there are going to end up being independent geographical enclaves designated in the aftermath of whatever is coming over the horizon. I, for one, would tell right-minded Californians to get the hell out while they can, because a wall dwarfing any other the world has ever seen is going to be erected about 30 miles inland from the shore, and we'll be
deadly serious about enforcing the crossing of it. Likewise with Manhattan Island and the coastal NW. These will be designated liberal Botany Bay colonies.
There are those who wouldn't like it if I were king.