What about NATO? Even without the US, NATO would still be the strongest millitary force on the planet. Since Canada is a member of NATO, anyone invading The Great White North would have to deal with most of Europe as well. The US would also have to leave/be expelled from NATO to declare war on Canada; its credibility and image would take a very long time indeed to recover (centuries).
By the way, I did hear once (I don’t have a cite on it) that Canada’s soldier are, on average, the best trained or almost the best trained in the world (better than american troops). I’m only talking about regular forces, though; I doubt we have any special forces that could compete with the navy SEALs or the british SAS.
Of course, Canada DOES have some pretty fancy nuclear technology (Isn’t the CANDU reactor the best nuclear reactor on the planet?). If things get desperate, a few covertly placed nuclear devices could make an example of america and show the world that Canada is in fact NOT a country that they wanna fuck with.
As for guns control…
The notion that guns in the hands of civillians would deter an invasion is ridiculous. For one thing, any resistance movement can get ahold of weapons quite quickly through the black market regardless of any gun control laws.
Second, even if your country were being invaded, what would you rather be: You could be harmless civillian; if an invading soldier kills you, it is an atrocity and will probably get the UN and NATO (even without the US) very angry at the invading country (NATO intervened in kosovo, didn’t it?). Either that, or you could be armed and dangerous. Since you’d likely have a gun, invading soldiers would shoot to kill on sight, no questions asked. Guns for civillians? Great plan.