Why are America's suburbs failing?

Cities exporting their greenery needs to suburbs is non-sensical, as lack of density in a suburban area makes any kind of access to a public park, even if it exists, a non-starter. Unless you reference golf clubs as green space, or sth. World's greatest parks are in deeply urban and dense areas - Central park in NYC, Jardin du Luxembourg in Paris. Oslo in Norway is 68% green space. Singapore is widely known as "garden city". It is demonstrably false to claim suburban areas are "greener" and that cities somehow export this need for an ammenity.

And no, it does not take suburban development for a successful city. The less of suburban development, the more destined for success a city is. I really hope you are not equivocating rural towns with suburban development. Rural towns in 1950s America used to have a train line, had town centres with dense development and streetcars were found in most of them. Suburban development is devoid of any kind of community, 3rd space building. The closest thing to dense centre is a stripmall. Many of which are detoriating in U.S. and have vacant units go unfilled for years.