The net result is that regardless of the second amendment (or Canada's stricter gun laws), neither Government is going to "turn on its citizens". The tendency towards tyranny, in my view, is an antiquity a this point. It's paranoia in a modern context.
Tyranny still exists on Earth. One of the most profound realizations of the founders of the American Republic is that they were aware of the tendency of republics to revert to tyranny, it's why they created checks and balances, the ones you consider to be outdated. The idea that becoming apathetic towards government would destroy liberty dates back to the greek republics of antiquity, which did eventually fall into tyranny. Who do you think would've predicted at the time that Athens, at its height, would become a tyranny, and a monarchy again?
I think it would facilitate a lot of interesting debate amongst the old enlightened thinkers if they could offer us their opinions today..
I think they'd point out how government restricting semi-automatic weapons, when both foreign and domestic standing armies have tanks, fighter jets, and nuclear submarines is a bizarrely unsubtle attempt to further pacify the citizenry.
You say it's silly to use resistance to tyranny as a defense of the right to bear arms, and I agree with you, in the sense that today, the government has the citizen so far outgunned, more than at any other time in history, that even with automatic small arms, it'd be a pretty futile affair. To be clear, your response to this is to give them more power, trust them with that power, and believe that everything is guaranteed to end well, because of all the achievements of the 20th century, changing human nature was apparently the greatest one.
We have a lot more to gain and a lot less to fear from joining together in collective governance than ever before. That means that the principles of freedom and liberty are working.
Government is force, every law is at its very root, a reason for the government to take away your freedom. What you're saying is the opposite of what is true. Government can only create freedom in so far as it chooses not to restrict it. In other words, government cannot give people freedom, it can only take it away.