I learned a few weeks ago that I'm a Canadian citizen. This was pretty surprising to me, since I was born in the US to American parents, but with Bill C-3 anyone with any Canadian ancestry is now Canadian. Perhaps you are too?
@jefftk Where did you get the estimate of 5-10% of Americans qualifying? The population of Canada is ~12% of the US population, so that would increase the population of Canada by ~1.5-2x, though I imagine practically speaking the vast majority of eligible people will not do anything with this.
I have nothing but a gut feeling to go by, but I suspect legal barriers to immigration are not the major reason preventing US citizens from doing whatever it is that Canadian citizenship allows them to do (work in Canada, vote in Canadian elections, etc).
@pganssle immigration from Canada to the US over the years has been maybe 1-2M. And then it's not just those people but all of their descendants, including ones with a very low fraction of Canadian ancestry.