Any rational assessment of Canada's military capabilities, its funding capabilities, and population will lead to a determination that they're not in any sort of position to have any sort of meaningful defense or offense without the US running point.
For that to change would require generational shifts in culture and revenue generation and so on. If the US chooses not to defend them, they're exposing themselves to unacceptable risk. If the US chooses to defend, Canada isn't contributing within the same order of magnitude. If the US chose to attack, then more has gone wrong in the world than you could possibly cope with, having a few thousand more tanks, ships, and helicopters isn't going to save the day. It'd take decades to build up population, R&D infrastructure, resources, and so on, and there'd likely be a lot of pressure to not do those things and use the US military industrial complex instead.
Not saying this is good for Canada, btw, just that the reality is they've kinda coasted on US coattails for decades now, and for better or worse, they're stuck. Which should in turn beg the question - if there's no practical or pragmatic point in spending a bunch of money on military preparedness and expansion, then why's that money being spent, and who's getting paid? Why are bureaucrats being militarized, instead of a discrete, well regulated military being created to meet whatever the need was?
Strange politics.