There's no reason for a country to be able to defend their airspace without the help of their allies? That's a defensible viewpoint of course, but the opposite is too.
Fair enough. It appears to me that Canadian fighters could have done it (see my other reply to the articles you posted), but it ultimately doesn't matter whether a US or Canadian plane did so, because air defense is shared. Recall that during the flight there was a period when a possible second balloon had been detected, and a US General, via NORAD, ordered Canadian CF-18s to search for it, as they were most readily able to respond.
If for some reason Canada felt it could no longer rely on the US for shared air defense, then I would agree with you that it would be important to build up domestic capability to do so independently—but as far as I can tell, that isn't currently a concern.
