I think an independent pro-British California is far more likely than a straight British one.
BUT, should it become British, I think that when Canada confederates (1867), there will likely be 2 dominions formed. The Canada we know and love, and a Pacific dominion that encompasses California, British Columbia and Vancouver Island. British Columbia wasn't overly keen on Confederation to begin with.
If the Civil War involves the British, the French also probably join. So now you've got British ships up the Californian coast, Sibley running around in the SW (in OTL, his campaign is almost hilariously bad IMHO), and the French coming up from Mexico. With Emperor Max being the navally inclined man that he is, maybe the British give Mexico San Diego and the Gadsden purchase region to shore up his reign.
BUT, should it become British, I think that when Canada confederates (1867), there will likely be 2 dominions formed. The Canada we know and love, and a Pacific dominion that encompasses California, British Columbia and Vancouver Island. British Columbia wasn't overly keen on Confederation to begin with.
If the Civil War involves the British, the French also probably join. So now you've got British ships up the Californian coast, Sibley running around in the SW (in OTL, his campaign is almost hilariously bad IMHO), and the French coming up from Mexico. With Emperor Max being the navally inclined man that he is, maybe the British give Mexico San Diego and the Gadsden purchase region to shore up his reign.