That will always be the big plot hole in EVERY zombie movie or TV show.
What starts out as a couple of zombies cant be stopped by 6 billion people? Please.
Yup. The vast majority of the living suddenly disappear in a matter of hours. As if no one has guns or ammo. And in a country this vast, the zombies always seem to mass around the survivors.
The only Zombie movie plot I ever found plausible was “28 Days Later” with the rage virus. A disease like that could actually have the advertised effect.
I kind of wonder if that’s what WWZ will be based on, as opposed to the (implausible) reanimated dead.
While I agree with both of your assessments, in part (not only armed populace, but also Spectre gunships and Daisy Cutters would wreck havoc on any swarming horde), keep in mind that over 6000 people die a day on average in the U.S. Immediate containment would be imperative, but not outside the realm of possibility in major cities for an outbreak to get out of control, at least initially.