The only two reasons for a citizen to own a firearm are for hunting or defense of the household from intruders.
I am going to add a third. Invasion by a foreign military power to take over the USA and boot out Donald Trump.
If that is the case, and let's say it's China with 300,000 active people in their military with another 5 million in reserve.
And let's say 1-2 million Chinese rock up in California and invade the country.
Now USA has 270 million guns, and let's say 90% of US people cannot shoot straight. That still leaves you 27 million people against 2 million Chinese troops.
Assuming the US armed forces sit on their asses, which is the only way the Chinese could conceivably invade the US, then I think the PLA Air Forces have more than enough firepower to flatten our cities and bomb us back to the Stone Age.