Agreed, although some sort of strange collapse in North Korean reason is possible but extremely unlikely with how locked in stasis they are - they're engaged in this weird ass stasis of Hollywood fascination and diplomatic sabre-rattling that they know affords their continued existence and duarchy with ROK; there's a couple of relatively "minor" powers out there that are major regional players that have access to nuclear stockpiles, aging or modern, that would be the most likely to start some shit.
Superpowers wouldn't dare start the apocalypse on their own, that's just fucking psychosis.
I think when I said 'limited', I meant an example incurring something like India and Pakistan, where I believe an eventual nuclear exchange is entirely possible - major powers won't outright fire their stockpiles but I have no doubts that Pakistan firing warheads is completely fucking possible, especially when looking at how deep they've dove into ultraconservative Islamism and anti-India sentiment in the past 10 years; otherwise, you're completely right - as for the rest of your post, I think a situation like the 'break-up' of imperiums is pretty much inevitable but I'm not sure that multiple American states will sustain themselves for very long without someone eventually reacquiring much of the country themselves; I guess total warfare still seems possible on a localized scale, but that's it.
Pretty much this.
Despite being the most destructive weapon ever made by man, nuclear weaponry has likely saved more lives in war if you look at it on a long-term scale.
I'm not so sure about NK, ever since Lil' Kimmy kicked the bucket and his sister took over, it's become more and more like a Chink puppet state.
If they do anything, it'll likely be at the discretion of the CCP.
Like everyone else has pointed out, if any country will launch nukes, it's going to be Pakistan.
North Korea is more or less kept on life support by China, and while I could see a second Korean War start up if things get desperate enough, I don't think NK will use nukes unless whatever Kim is in charge has no Chinese support and realizes the DPRK is done for and decides to literally go out with a bang by recklessly launching whatever's working in their arsenal at South Korea, Japan, and possibly Guam as one last middle finger to the Americans/South Koreans/Japanese.
In that astronomically unlikely scenario, NK will also launch whatever conventional and chemical artillery, rockets, and missiles they have in addition to the nukes since Pyongyang would be collapsing anyway.
In reality, Kim Jong Il pursued the nuclear program because he knew it was the only way to keep the ROK and USA from finishing what General MacArthur started back in the 1950's, especially in a world where the Soviet Union was gone, the North Korean economy was virtually non-existent, and even China was increasingly becoming economic bedfellows with the United States and Western Europe.
As idiotic as Kim Jong Un is, even he knows the nukes are meant as little more than insurance for the regime's continued existence.
Pakistan is the only country that I can see launching nukes, and a nuclear dust-up between Pakistan and India is also the least likely to kick off a complete apocalypse, unlike a nuclear war started by pretty much any other country.
None of the superpowers (United States, China) or world powers (UK, France, Russia, Iran, Israel) want to be the ones who are responsible for "When The Wind Blows Part 2: IRL Boogaloo"
Iran may be an authoritarian Islamist oligarchy, but they are considerably more restrained than Pakistan, namely because they have more at stake given their oil fields, mineral resources, and Tehran's influence over the wider world of Shia Islam and Israel has an autistic fixation on self-preservation of their state at all costs.
Israel is only going to use their nukes if the shit really hits the fan and they really know for sure their state is truly doomed and want to take as many of their enemies down with them and Iran is likely in a similar situation along with having a similar "regime insurance" motivation as North Korea does for its nuclear program.
