[alistairSH]

Depends how you define "downtown"...

Most US cities have a central business district that is majority commercial office space, with just enough retail/dining to let workers take lunch breaks. These are the areas that are dying. No workers, so the surrounding retail/dining is failing.

Back in the 50s/60s, white flight was a problem for cities - most of the middle class, white families moved to the suburbs. Most cities didn't have a large tax base that lived inside the city. That started to change over the last 20 years or so. Couple that with off-shoring or moving of heavy industry out of city cores and cities will struggle financially without white-collar/knowledge workers commuting in and spending money.

Western Europe doesn't have the same level of suburban sprawl.

Edit - the white flight I mention is closely related to the inner-city highways mentioned in the sibling comment. Suburban workers needed to get downtown, so (usually minority) neighborhoods were split in two or destroyed to built highways from the outskirts into the CBD.