Both make it clear that should something cataclysmic befall us all we'd be faced with the near-impossible problem of restarting agriculture. Modern, surplus-generating, agriculture isn't possible without modern society, starting with the basics like fuel and fertilizers (and everything else that's connected: the rule of law, supply chains, logistics, PhD-level domain knowledge and expertise, and so on). Those who survive "the event" would be forced into a life of sustenance farming for generations - and while you might think some semblance of modern civilization could be reestablished within a few years, consider that if everyone is sustenance farming for themselves, that leaves almost no-one left to do the actual reconstruction work, and that includes rebuilding fertilizer plants, fuel refineries, oil extraction, and agricultural machinery production.
Without anything close to today's industrialization and automation being restored within a few years (hint: very unlikely) it only gets worse: our modern society depends on an educated workforce. Under a "everyone sustenance farms for themselves"-scenario that means there's no-one to sufficiently educate the tens of millions of school and university-age people, assuming those kids aren't press-ganged into farming for their local district before they can even read or write, so with that outlook what hope is there to rebuild and operate oil refineries from scratch?
And "rebuild from scratch" is the word. While Russia might no-longer have enough strategic warheads to completely obliterate the northern hemisphere (at least for now), I'd bet a week's worth of my future postwar turnip ration that Russia has all of North America's oil refineries and related infrastructure marked as primary-targets, such is total war - so in the aftermath it definitely wouldn't be as simple as reconnecting some broken pipework and wiring-up a generator: the entire gulf-coast's set of oil refineries would be obliterated.
So, yes, you're not wrong: we will all band together, but I'll add that we'll band-together for a world of suck for 10-20 years before we mostly succumb to then-untreatable cancers, and our offspring will grow up as illiterate and uneducated serfs.
I must say, relocating to Chile or New Zealand is looking very attractive right now...
