Just to clear the air, I too am a Canadian, one who looks to the USA for a model of responsible government.
The bad guys of this world see Canada and the USA as about as different as Coke and Pepsi, and have referred to us as, variously, a mini-Satan, a place where boys get indoctrinated into homosexuality by their 13th birthdays, and (of course) an imperialist aggressor (because of our peacekeeping presence in Afghanistan among other things). Al-Qaida has sworn that it will "bomb Canada into the stone age" (their words) when it gets the chance.
Were it not for the American defense apparatus, eventually Al-Qaida would likely have acquired the resources needed to make the dream a reality. Sooner or later, Bin Laden and Saddam would have come to the realization that they hate the West (North America in particular) more than they hate each other. Would they have been able to invade ? Probably not. Would they have used Iraqi State resources to develop nuke/chem/bio weapons for use in terror attacks ? Yes.
It would have put an awful strain on the health care system if nuke bombs or plague carriers were set off in downtown Toronto, Montreal, and Vancouver at the same time...
Assuming it is true that we purchase crappy socialized health care at the expense of defense, I say that we've incurred an additional cost: the loss of our national dignity. It's downright humiliating to hear Americans say that we sleep under the blanket of security they create- knowing that it's true. Why should we have settle for being a "mini-Satan" in the eyes of the bad guys and "America Jr." in the eyes of the good guys ?