Russia is on the UNSC and they have never been recognised as UN members formally. The relevance of the UN in NY would die immediately anyway. The rest of the world would embrace their new Californian friendo. Because shared morals and culture. Californians have more in common with the rest of the world. California might join the EU even, with Canada and other states. And really what are red states going to do about it if it happened all at once? It wouldn't fix everything but it would fix A LOT!