I disagree. I think that Canada could be a major player in manned space exlporation if it wanted to be. The Arrow conclusively demonstrates that Canada is capable of conducting advanced technology research without relying on outside funding, or having to partner with another country. The Arrow was first the jet fighter designed to fly at high mach speeds and was the first jet fighter to integrate fly by wire technology. The Arrow was so advanced that the major American, British and French aircraft manufacturers patently said that it could not be built, and would not fly.
The problem is that major space exploration is very expensive and difficult (look at the amount of funding that both the Soviet and American programs got--it was quite a lot, even after the end of the Space Race). Canada doesn't really have the funds to compete, and without some other attractor they're better off working with the US than trying to build their own program.
That said, Canada certainly could do more. They have enough money to do joint US-Canada interplanetary missions, or to have Canadian astronauts (earlier than OTL, anyway).