The good news is that a substantial chunk of the world's cargo transportation runs on diesel (or other combustion setups similarly not reliant on electronics), so in a pinch it could probably keep going. Same with agricultural machinery. Might need to replace or refurbish some ECUs, but I'm sure there are enough clever mechanics out there willing and able to bypass those in an emergency that we'd be back up and running pretty quick on that front.
ICE 1, electric 0 ;)
It's refrigeration that'd have me more concerned, since pretty much all modern refrigeration is electrically powered (last I checked). Diesel generators might come in clutch there, assuming the refrigeration units themselves don't rely on any fancy electronics.
Worst case it sets us back to 1870ish, maybe. Depends on how fast things go to crap vs how fast things can be rebuilt.
Likely case you'd basically get a "purge" because society as we know it can't keep on rolling with the kind of economic breakdown something like that would cause so there's be a lot of dying in the interim but if you don't starve or get shot in the first 6mo you're probably good with the very old, very young and unproductive bearing the brunt of it (same as every other disaster) It would be like the black death, but global and all at once. Balance of power globally would definitely be altered in unforeseeable ways but the overall net result is things would bounce back hard.
Yeah, but those individuals were presumably all in pretty close proximity to one another. If we were left with a few thousand individuals across the entire range of the human-inhabited Earth, we'd have one heck of a time continuing as a species.
In any case, the risk of an extinction event on Earth is exactly why I believe space colonization needs to be Priority Zero for humanity, from two different angles:
1. Living beyond Earth means that we as a species are that much more resilient against a literal-Earth-shattering catastrophe (and if we can get the bulk of Earth's current/future population off of Earth, then we might very well be able to avoid a couple different plausible extinction events).
2. If we can colonize entirely inhospitable worlds like Mars or the Moon (or my votes, Ceres, Venus, and Enceladus), then "colonizing" Earth is easy-peasy-lemon-squeezy even if it does become Venus 2: Greenhouse Boogaloo.