There may be a period where the renegade province tries to go it alone but eventually, it will discover that it is better off in the USA.
We had better be very selective in which ones we would allow in. The Maritime Provinces are full of descendents of people who left this country - before it was a country - because they sided with the British. Quebec is and will always be French. Ontario is Massachusetts North.
If you want to see a socialist United States, bring them all in.
I love Canada, it is my second home. but I don't think many appreciate how deep the hatred of America among much of the Canadian population is. There would be consiterable violence, not to mention 30 million more democratic voters.
I don't think there is any real possibility of even Quebec leaving Canada, as for Alberta it is even less likely. and although Canada is independant, England wouldn't tollerate it,
Kyoto isn't popular, but it has become an article of faith to the 3rd term Canadian prime minister who after 10 years in office still hasn't been able to come up with a legacy, his Liberal heir Paul Martin has suggested to the oil industry that Kyoto is good as dead.