yes, I totally understand that. While they are separate countries, their economies and supply chains are extremely closely tied together and closing the border to US people would cause an extreme econ shock in both countries. Retaliation from the US would probably be stupid, out of scale, and make the situation much worse. My whole point is I don't think Canada would risk it.
I hear you and I think that's part of the reason US folks are still being allowed up - but honestly, there's a pandemic on, Canada shouldn't be held responsible for making sure Trump doesn't look bad and end up flipping out unreasonably - that's America's problem.