Don't most Americans live in cities, now? Dallas has awful public transportation, but hypothetically, you could use it to get to work - it would just turn your 30-60 minute commute into a 2.5 hour adventure.
But the problem is that public transport goes near where lots of people want to go but doesn't go where any person actually wants to go. This means further traveling time after the public transport bit is finished. And probably connections as well. This means, for me, that public transport takes about twice as long to get anywhere.
In my opinion the future is robot controlled cars. All the benefit of public transport with none of the inefficiencies, etc. Public transport is just an intermediate step.
That said, many offices have reserved parking, which fixes this - though that real estate is valuable.