I'm not entirely sure. The big question would be whether the Dominion of Oregon (or whatever it's called) ends up merging with Canada or whether it maintains a position as a slightly culturally different governmentally distinct entity. Assuming Oregon and the Sandwich Islands end up grouped together under one government it would provide the Pacific Northwest with an invaluable coaling station/naval base. Although Oregon would likely not be able to fight off a Hawaii fillibustering attempt on its own if the British fight off a few attempts before it spins off its Pacific territories the two Dominions could remain united into the modern day.