(144) Retrofitting near Paris

Retrofitting seems to be the suburban-poverty theme of late.  Here is a link to an article describing the benefit of changes to Plessis-Robinson.  An outer suburb in southwest Paris, France.  What is referred to as “smart growth” or “new urbanism” in North America was put in place there beginning in the 1990s.  The article, like much discussion of suburban futures, is mainly about built form and resource usage.  Again, who would argue with attractive buildings that conserve energy, greenspaces, walkability, public safety, advanced recycling, water saving efforts and so forth?  Well, only an idiot.  What is it then that retards such development in one place but not in another?  See the results for yourself in the six minute video available at the link below.
It would seem to us that improvements to sustainability and general aesthetics might make a suburb more expensive and harder on those with less income.  On the other hand, denser, more economically diverse places with better public transit and a variety of types of housing would make life easier for working people and those in social difficulty.  How late is it to be putting in place a process of working out such issues in North America?

Can US communities learn from this European suburban retrofit? NRDC website