Not necessarily borders, but I think being in the same geographic region helps. For example, Canadians interested in making TV shows might find more collaborators and funding in Los Angeles.
Technically, especially with the internet, there is no reason a Canadian show made in Canada could not be a hit in both countries. It is just the likelihoods that change.
The slight bias against Canadian shows is that if they have Canadian-specific content (e.g. city, backstories, characters) that are an important part of the story, then the larger American audience will be much less likely to find it interesting.
The inverse is not true however -- the article is correct that Canadians are exposed to (almost too) much American content from an early age, leading to the Canadian Radio-Television & Telecommunications Commission (CRTC)[1] to adopt (read: mandate) minimum ratios for Canadian-specific content to be aired.[2]
Technically, especially with the internet, there is no reason a Canadian show made in Canada could not be a hit in both countries. It is just the likelihoods that change.