I can tell you about St Louis. The metro area keeps growing, albeit slowly. The city isn't, and it's been in trouble for decades. The main secret here, and what makes St Louis top lists of crime, is that the city itself is quite small compared to the metro area itself, which makes comparisons with unified metros be anything but apples to apples. This separation is also key when it comes to the failure of the city's government.

St Louis city was separated from the county in 1876. Describing the full details would take forever, but even back then, the issues were clear: The issue is the city carrying costs, while suburbs get the benefits. This is still true today: The metro area is now made of dozens of municipalities, each of trying to have lower property taxes than their neighbors, while trying to beef up their economics via sales taxes, which are paid by people that are often outside of that municipality. No suburb has property taxes that cover their costs: This is why we have unincorporated land, as absorbing it would be negative to the bottom line. This is also why there's such a high pressure on police as a form of revenue: As highways were built in ways that gave small sections to many municipalities, so they could raise money from people that just pass through.

The city has been badly mismanaged: Its redevelopment, not unlike that of most US cities, has been mostly for the pleasure of suburbanites that might work there. Wide, fast streets that are about as pedestrian unfriendly as you can get, over 30% of downtown space dedicated to surface parking or buildings solely dedicated to parking, green areas that are overly large, and office buildings with no commercial real estate in the first floor, there's really no reason to spend a second walking the streets, barring a few very narrow bar areas. Every single thing that makes the suburbanite worker's life easier also makes living near downtown worse, which is why few people live downtown.

There are a couple of areas, further from downtown but still within the city limits, that are doing relatively well: They are the ones that have narrow, streets, relatively well mixed zoning by US standards, and where real estate prices are moving up. Decent dense urbanism leads to working businesses. Still, everyone needs a car, because outside of said small enclaves, it's really hard to move without one. There's also the schooling problem: In practice the affluent in St louis have abandoned the public school system, and just have private schools for whatever preferences you wish. High academic standards, diversity-focused, aiming at ivy league universities? Yep! Traditional, gender segregated religious schools, teaching "traditional values", no problem. Your school can be 95% white, 70% asian, 99% black... just don't expect a usable public education unless the average house in your district is $400k.

I've lived here for over 20 years, and compared to even declining cities in Europe, what is so amazing is how fragile the economic network is, how little you can access if you walk a mile from your house. Even today, it sure seems that development decisions are made thinking of the people that live in a neighboring municipality, instead of local residents.

So what is killing St Louis City, other than mismanagement? That a small army of little suburbs are doing their best to capture its tax dollars, while taking advantage of its services.