system
Given the following post, respond as if you're commenting on Reddit:
human
[World War Z book] how long is the reconquest of America going to take?

The book describes the US government regrouping on the west coast and building a war economy in order to take back the country.

How long is this going to take? Ten years? Twenty?

Will people's grandchildren still be fighting zombies?

I think the problem with America is that it's way too big. By the time the government can reach the East coast there is going to be hundreds of small kingdoms already running all over the place besides the zombies.

Also, the book describes the first battle against the zombies as a British style square where soldiers shoot until they are walled inside mountains of corpses.

Is that really the most efficient way to take zombies out? Hundreds of soldiers means a lot of food, ammo and fuel for their vehicles.

I would have rigged abandoned cars with fog horns and TNT. Once a sizable horde shows up just make it explode remotely.
gpt
Zombies are going to be a fact of life *forever*; all it takes is one wandering out of a cave or onto a beach to start a local incident, and if the initial response is botched you can have a big problem on your hands in short order. Constant vigilance becomes the price of civilization.

RE: Car bombs, you're going to liquify the closest zombies, leave the surrounding zombies maimed, and the ones behind those intact.  Assuming you wait for maximum density around the bomb, the ones in front serve as a meat shield for the ones in back, protecting them from blast and fragmentation.

Fighting squares aren't glamorous or fancy, and if a square breaks the body count is atrocious, but they get the job done. Each Z gets a headshot, no muss, no fuss, no combing through a pile of shredded long pig to find the Zs that just have fractured spines or torn-off legs. 

Independent kingdoms? That's what the tanks are for. Any survivor community that doesn't want to play ball gets an object lesson in combined-arms warfare that they are not equipped or trained to cope with.