Futurely the populational trend will be even more favourable to Canada, and the more or less mixed pattern of settlement may help forge a strong national identity, by not having anyone with strong majorities in most places.
There are also interesting implications for the future of other Dominions.
Archangel
That's probably the most important change in the scenario. Given more land and more rapid economic development, plus the hostility of the US, Canada will reach an economic breakthrough point so that even if relations with the US improves and it develops rapidly itself it won't drain off population and investment from Canada. With the higher rate of immigration and greater prospects it could well surpass the US in economic strength by the end of the century.
Interesting that despite the highly flow to Canada the cut in movement to the US means a boost for the other British settlement areas. S Africa could be especially interesting.
Steve