3 drinks later and I'll vomit a random plot involving a self-driving drone exploding in the midst of a parade, killing a local warlord and starting-off WW3 (except it barely leaves North America, and somehow involves niether Canada nor Cuba).
Flash-forwards 82 hours later, America is in complete shambles, what remains of the electical grid is substandard, there's metal-fatigue on all levels of the government, and the nieghborhood vaugely resembles the demilitarized-zone (dogs and cats sleeping together, total anarchy).
So now it's you, your best friend, and some beat-up relic of a giant American mecha to help rebuild Mexico's border-wall to keep the radioactive-zombie-epidemic out.
Oh, and there's rumors of enemy catgirls in the area... nobody has seen any yet... probably just some urban-legend wartime propoganda.