Can someone put Pompeii in context? How big of a city was it, say compared to cities in the U.S.?

If you consider how the town was a port town/holiday resort known for its cheap/lower class brothels in an area prone to earthquakes and that by the time of its destruction in 79 AD a good chunk of the population had evacuated (not to mention that reconstruction from the 62 AD earthquake was still in course), in the grand scope of the Roman economy I would say not much at all. Pompeii wasn't the sole holiday spot in the Roman Empire so those that wanted to enjoy the seaside moved somewhere else to enjoy their whores and wine. Heck, Pompeii wasn't even the wealthier one out of the cities destroyed by Vesuvius in 79 (way more expensive homes were found in Herculaneum, Stabiae had luxurious villas along the coastline, Boscoreale produced fine wine, fruits and olive oil) or had VIP villas (Oplontis had a huge villa commonly associated with Nero's famous second wife Poppea), the Roman economy wouldn't be dependent on the lives of the poor/ill that did not leave or were left behind to die an horrible death in Pompeii and whatever industry/wealth production that the city might have had, I guess (and this is only an assumption, I don't think there are reports about it, Plinius the Younger did not bother to write about that part apparently) it wouldn't have a great effect in the overall Roman society too, aside from the dramatic depictions of its demise.

It is thought that a lot of elite wealth evaporated in the eruption, not in Pompeii itself but in the surrounding region where a lot of senators and even the imperial family had villas, and it has been suggested that wine-production in certain regions (notably Gaul) boomed after the Vesuvius slopes got out of use, but that's of course hard to measure unambiguously.

What is certain is that repair works, not in Pompeii (which was of course abandoned) but in the wider vesuvius region cost the Roman state a lot of money and manpower. There is epigraphic evidence for that in cities like Naples, Nola, Nuceria and Sorrento.