The jobs are in the city because the people are there, and the people are there because the jobs and other people are there. Empirically, both residents and employers prefer to relocate to the city.

The city is convenient and fun: it provides easier transportation, more amenities, more other people to engage with, more companies of all types to do business with, etc.

You ignore the fact that many European cities are much smaller than the North American mega city landscape and still have lots of jobs in those cities. But it's also easier to have safer yet walkable and publicly transportabel neighborhoods in a city of 150k or 300k than 3 or 10 million.

There's plenty of American cities from 50k-300k, that's not a uniquely European thing.

None of the jobs where I grew up were in the city (Allentown/Bethlehem/Easton, largest employers were all suburban campuses save for the electric company and some colleges. Even the hospitals were off the highway.).

All the fun stuff was in the city though, so that's where we'd go once you got a friend of driving age.

If you run a business selling a niche amenity, you need to do so in a city because in the country you won't have enough customers nearby.

End result: cities have more fine-grained amenities. People who want more amenities live in cities.

There are? I see the opposite trend (at least in US East Coast) - cities only have generic amenities, while all the unusual stuff is in the suburbs, where the the land is cheap.

For example, let's take a relatively common hobby of sewing. The two stores in downtown closed tens of years ago, and the only ones left are in the suburbs, unreachable without the car.

I think at this stage, the only advantage of city is bars, restaurants, and expensive clothing/jewelry. If you like something else, you are better off in suburbs with a car.