It is true that while the US army might have the most guns in the world, the US public seemingly isn't all that far behind. Even if your armed forces were not allowed to take part, you'd still probably win in a land war against Canada or Mexico.

I don't necessarily disagree, though I seriously doubt Canada or Mexico would ever invade the US, as there would be too much to risk and too little to gain for the cost. The sad thing is, and I feel really strange saying this as a former member of the US military, we also are supposed to be able to combat our own military should they one day be used against us. Though the US military has not been used against the people of the US since Posse Comitatus (excepting recent drone strikes in foreign countries), history (and present day) is full of examples of this not always being the case.

I don't think you can talk about the point of the second amendment completely without mentioning the fact that it was envisioned to apply against both foreign invasion and domestic tyranny. I'm pretty sure 'self-defense' was a given to the founders, and did not enter into the thinking for it - they were explicitly laying out out the need for civilians to be able to rise up against their own government.

Jefferson's famous quote, "the tree of Liberty must be refreshed from time to time with the blood of patriots and tyrants" is actually a smaller snippet of a quote which speaks directly to this:

"God forbid we should ever be twenty years without such a rebellion. The people cannot be all, and always, well informed. The part which is wrong will be discontented, in proportion to the importance of the facts they misconceive. If they remain quiet under such misconceptions, it is lethargy, the forerunner of death to the public liberty. ... And what country can preserve its liberties, if its rulers are not warned from time to time, that this people preserve the spirit of resistance? Let them take arms. The remedy is to set them right as to the facts, pardon and pacify them. What signify a few lives lost in a century or two? The tree of liberty must be refreshed from time to time, with the blood of patriots and tyrants. It is its natural manure."

Hollywood movies do a pretty good job of reminding the US public of the facts of the cruel world out there. Well, the paying US public. Hold on a mo', perhaps there's a case here for allowing unrestricted access to such movies to those who can't afford it, or would rather buy something else. Unrestricted access via, say, Megaupload.