after all the time has passed I'd assume most firearms and ammo were first gathered by the military and then the military broke up sue to the incompetence of the walking dead series horrible military leaders (its a movie and the military loses obviously for plot). The survivors likely gathered the weapons back and took them to their own respective groups and communities. the military planes, jets and tanks don't last forever
the one guy who drove a tank in the waling dead seemed to be a runaway from the military that lost most discipline and his marbles to an extent.
in the game "the last of us" the military only some controls the major cities/highways and scavenges the suburbs for supplies sometimes but their are smaller groups of hostile survivors friendly and hostile that moved into the mountains and harder to reach places. All the shtf shows have the military control the big cities and show they can't control the wilderness very well
the one guy who drove a tank in the waling dead seemed to be a runaway from the military that lost most discipline and his marbles to an extent.
in the game "the last of us" the military only some controls the major cities/highways and scavenges the suburbs for supplies sometimes but their are smaller groups of hostile survivors friendly and hostile that moved into the mountains and harder to reach places. All the shtf shows have the military control the big cities and show they can't control the wilderness very well