Earlier quoted context omitted.
I think the collapse of the US as "The World's Policeman", will result in the most nuclear proliferation since the 50s. That alone will make the world a much, much more dangerous place.
Why more dangerous? I am worried about religious fanatics armed with nuclear weapons. I am not really worried about Germany, South Korea, Japan or Taiwan armed with them. The more deterence, the less likely there will be a war. You go to war when you think you can get away with it, not when you think there is even a 10% chance all you major cities will be nuked.
You should be. The more small states with nuclear weapons, the more chances there are that any one country feels like a nuclear assault could be "worth it". Heck, just look at India and Pakistan. I can't remember which Indian government minister said it, but years ago he essentially said that India could "absorb" a nuclear strike from Pakistan, because since India is bigger with a lot more people, any nuclear volley would mean the complete annihilation of Pakistan while India would "only" lose a couple hundred million people...
The more proliferation there is, the higher the chance any one government will move away from MAD theory to "well, guess we've got nothing left to lose".