There's no prohibition for remote work per se. The American company just needs to set up its legal presence in Canada since only Canadian companies can sponsor

There's no prohibition for remote work per se. The American company just needs to set up its legal presence in Canada since only Canadian companies can sponsor immigrants. That would still be a barrier to small companies so I expect the PEO (Professional Employment Organization) industry to come up with a way to make this possible at any scale. And that's before Canada changes IRCC regs to help this use case, which they could very well do.