There are significant differences between Vietnam, Afghanistan, Iraq and the modern day US. You're simply kidding yourself if you think that the average American citizen would be ready, willing and able to take up arms against the military.
Also, yes, it was insanely important in 1776. It's far less important now. Again, I'm not even for heavy
And 1940 America and 2015 America aren't vastly different? Both in military might and make up of the population? Not to mention technology employed in conflicts?
Come on you guys. I'm not even against you on this. I'm just against this reasoning that you need your 9mm or 12-gauge or AR-15 because of the threat of a tyrannical government (either from within or from outside). It's such a laughable argument.
And again, the territory outside of Kabul and Naperville are different animals. If the US Government actually turned against the US citizenry, it would have to be under such outrageously ridiculous circumstances that they wouldn't hesitate to go total warfare, and you're not doing much against the US military at that point.
We will just have to agree to disagree on that point, hopefully we never see it come to that.
One other thought relating to that subject, I believe another aspect of the 2nd Amendment is just as important as the practical side. The 2nd helps give considerable pause to any aggressor. Whether that be a tyrannical government or a foreign threat, they have to consider that there will be many thousands of people who can and will fight back.