Gun ownership in the US is largely correlated with where someone lives. A lot of non-Americans forget that the United States is really just 50 very different states in a trenchcoat all pretending to be a single unified country.

Southern states have tons of gun owners, while they're much rarer in northern states outside of more rural areas. The type of gun owned also depends, with a single concealed carry pistol being far more common in cities and the north, while gun nuts tend to collect everything from rifles to shotguns and often have several boxes of ammo for each.

Unfortunately the areas with higher gun ownership tend to be the conservative ones, which doesn't bode well for any civil conflict. Not to mention police forces everywhere lean heavily conservative and are armed to the teeth with military surplus gear due to our many wars and lobbying from the Military-Industrial Complex, up to and including SWAT teams with APCs.