The nukes that actually exist today would reduce us to a medieval or early industrial existence, except with a lot of information about how to rebuild faster — Hiroshima and Nagasaki both got rebuilt and are now thriving, and while modern weapons are higher yield and much of the industry to rebuild with would be destroyed, not all of it would be, and roughly half the global population would still be alive to do it.

I wouldn’t count that as “effectively destroy us completely”, even though it would be really bad.

Keep in mind that all the easily-mined coal, oil, and gas deposits have been used.

We might be kinda screwed if something takes out civilization (e.g., the nukes fly).

I guess we can hope that nuclear winter is exaggerated or non-existent and the southern hemisphere pulls through with intact infrastructure after the exchange.

Sure, everything would suck for a while[0]. But we had wind and hydro for a long time before electricity and steam, so those that survive could rebuild, analogously as to how we are presently weaning ourselves off fossil fuels without such destruction.

[0] I realise given the context of global thermonuclear war this may seem like understatement. Well, I’m British and I have a stereotype to uphold.

It might not be as easy as you'd hope to rebuild.

This essay does a good job of explaining why it's probably possible in principle and why in practice it might be quite difficult:

https://aeon.co/essays/could-we-reboot-a-modern-civilisation...

(Incidentally, I highly recommend that author's book _ The Knowledge_, which is a more extended meditation on industrial civilisation and what it would take to reinvent it if we lost it.)