However an all-out war between the U.S. and the U.S.S.R in the 1980s most certainly could have.
Why do you think this?
Because all the evidence I've read or heard (most of it back in the 1980s) agreed on this. Specifically in a likely exchange between the U.S. and the USSR the northern, hemisphere would have been rendered completely uninhabitable within days. Humanity in the southern hemisphere would probably have lasted somewhat longer, but still would have been destroyed by nuclear winter and radiation. Details depend on the exact distribution of targets.
Remember Hiroshima and Nagasaki were 2 relatively small fission weapons. By the 1980s the USSR and the US each had enough much bigger fusion bombs to individually destroy the planet. The only question was how many each would use in an exchange and where they target them.
One open question in AI risk strategy is: Can we trust the world's elite decision-makers (hereafter "elites") to navigate the creation of human-level AI (and beyond) just fine, without the kinds of special efforts that e.g. Bostrom and Yudkowsky think are needed?
Some reasons for concern include:
But if you were trying to argue for hope, you might argue along these lines (presented for the sake of argument; I don't actually endorse this argument):
The basic structure of this 'argument for hope' is due to Carl Shulman, though he doesn't necessarily endorse the details. (Also, it's just a rough argument, and as stated is not deductively valid.)
Personally, I am not very comforted by this argument because:
Obviously, there's a lot more for me to spell out here, and some of it may be unclear. The reason I'm posting these thoughts in such a rough state is so that MIRI can get some help on our research into this question.
In particular, I'd like to know: