in fact, california has more people than canada and a bigger gdp, too. californians may be exaggerating the importance of canada by it's relative size and desirable social systems; the truth is that a merging of california and canada would be one in which canada would be the junior partner - we would more accurately be talking about canada joining the united states of the pacific coast, and that's not something canadians are going to go for.
if california were to separate from the union, it would be better off going it alone - and it would probably take at least nevada with it, too, along with oregon and washington.