Even more so, this is plain impossible.
At least with Canada, you had a) a direct, somewhat open border with a neighbor with a large population, and b) a hell of a lot closer to Britain and Europe.
With an even more hostile environment (at least in cold, you can wear as much as needed (to a certain degree)), with natural hazards which are pretty damn real, and isolation from basically everywhere else (minus Indonesia + the Pacific islanda), 300 million with a POD before 1900 is downright impossible.