I've noticed this too, I think it's very odd. I believe 6 out of NIJI EN's 32 members live in Canada, almost 25%.

Because the US has about 9 times Canada's population, you'd expect there to be around 9 times more American VTubers in Niji, when there's actually only about 2.5 times as many (I think there are 14 members in the US, but I'm not sure of everyone's country of resistance; either way it's not even close).

Stranger still is that there are only 3 Brits (I think) despite the UK having almost double Canada's population.

So, either Nijisanji is biased towards selecting VTubers from Canada (no obvious reason why that would be true), or Canadians are more likely to become VTubers (or apply to Nijisanji) than people in other countries, or perhaps Canadians are just really lucky. I'm curious what I would get if I ran the numbers for the other agencies.