You do reduce it when you bring a gun to a tank / plane / automatic weapons fight, rather than a knife. It isn't meant to provide all the armaments you need, but it leaves you a starting point.
An already economically-weakened ConUS can expect the following: A domestic military with hardware that is failing left and right. A domestic military that has no ammunition because the "domestic security forces" bought it all. A domestic military that has no fuel. Foreign Fighters that are well stocked and equipped with advanced weaponry.
The real "rulers" don't consider this to be their own country. They are citizens of the world. ConUS contains several million nuisances that would be best killed in an expedient manner, such as by plague or nuclear attack.
In that kind of environment, it is less likely that having an AR or an AK in the attic will help the typical USian.
Anyone with nitrogen fertilizer or many, many other household items can "start a one-man war," but they likely will die just as quickly.
At the risk of quoting Yoda, wars don't make you great. But more to my point: the best offense is a good defense in politics.
I don't understand why people keep asking this question, and variations of it, or offering up the argument "the 2A is useless for allowing rebellion since you can't defeat the US military".
Bands of rebels armed with mostly light weapons have caused superpowers all sorts of issues: See Afghanistan, from the Soviet era through today.
And if a full fledged rebellion did break out in the US, here are a few points to consider:
1. It's likely that at least some military units would side with the rebels. So you're already not talking about a case of just "you and your AR-15 versus tanks and F-16's".
2. Nukes are effectively "off the table" since there wouldn't be much point in nuking your own country, as there wouldn't be anything left to rule.
3. A hypothetical rebellion would not be limited to just AR-15's and what-not... factor in IEDs and various kinds of improved weapons.
4. And factor in stolen / captured military weapons.
5. And factor in military weapons provided, illicitly, to the rebels by the manufacturers, distributors, foreign groups, and gosh knows who else.
6. The population of the US is somewhere north of 300 million people, right? And a significant portion of the population own firearms. How many members are in the standing US military? According to Wikipedia, there are 1,429,995 active duty members of the US armed forces. IF a rebellion had sufficient popular support, consider, as they say, that quantity has a quality all it's own.
Anyway, the point is to say that it's not as simple as "you and a gun versus the US military" if you look at the big picture. I mean, sure, if it's just you and you take on a tank with an AR-15, they're just going to run you over, game over. But if an actual, massed rebellion, with lots of popular support were to break out, those guns do matter.