Immigration in my current game of Vicky (playing as Canada from 1840 onward) is...well a mess. British Columbia receives ALL of the immigration within my game. Ontario has received some (some Russian Orthodox farmers, scripted events from the VIP mod...or from the original, I dunno) as well as Alberta and Manitoba (not sure how, but they had a small boost until it stopped).
Right now, British Columbia has absolutely no industry, for the fact that the capitalists builds where factories already are (New Brunswick, Ontario, Quebec) but not where the population s (BC, Alberta, Manitoba, Nova Scotia). I've tried creating capitalists POPs in BC, but they had no impact. Things like social reforms (Which was at good before the immigration went bonkers) are now too expensive as I have dozens of usuable POPs in BC (clerks, factory workers) because I can't seemingly figure out Full Citizenship.
I like a few ideas that would make immigrants move to areas where there are jobs, or at least internal migration, but whatever the programmers choose, don't leave it as is.
Edit: AT LEAST make capitalists build factories where there is a large number of POPs then.