I doubt western Canada would become a separate dominion. If Canada doesn't take it the most reasonable assumption is that is bc the USA already did.Title pretty much says it all, if Canada never expanded beyond the borders of the original province of Canada from 1840 for whatever reason and eventually became several separate dominions and independent nations what happens the the sparsely populated (except Winnipeg) central Canada? Does the Hudson Bay Company become a country eventually? Do the aboriginals get all or at least part of it?
A big part of Canadian unification was the American threat so if for whatever reason the US was seen as a non-threat (maybe the US splits early on, or there is no manifest destiny) Canada might not have unified.I hate to give the dreaded non-answer, but I think it depends. Why didn't it expired? Was BC deemed to be self-sufficient? Then the prairies might be joined to them. Or they might have both been lost to the US. If do truly stay independent, they might go the rout of newfoundland, barely being self-sufficient
The Canadas had their eyes on the prairies for a long time and they were gearing up for expansion well before Confederation happened. Even if there are a bunch of separate dominions the West (excluding BC) probably still winds up in Canada.