[zepto]

Commercially available guns are the same or better as the guns used by US soldiers for the most part.

If you are talking about the US military doing aerial bombardment etc, of course these guns will not be a defense.

But if troops are going street to street, commercially available guns would enable resistance.

And the point here is not that the population would be able to win an all out war against the fully equipped army. That is a nonsensical scenario. It is that an armed population would be able to resist the Army, making all out war the only option. US army won't launch an all out war against the population, so this level of resistance is sufficient.