The Guardians of "TOWER" TGO"TOWER"

Back in 2013, the US government sliced off a chunk of NYC and handed it over to the superpowered bunch, forming this place called "TOWER" It's just ready for superhumans—no regular folks allowed.
Then, in 2014, other countries started copying the US move. Similar mini-cities popped up in those countries too, but only in the wealthy ones.
Fast forward to 2023, when World War III explodes. Nuclear weapons turned the air into a slow poison, choking everyone. Those sliced-off cities were safe havens. They had these unbreakable shields that kept the nastiness out. So, all the survivors got ushered into these government-guarded cities.
Our story takes place in "TOWER"