how did inexpensive cars and gas prices affect the developement of the US?

Answer 1

I would say that the one of the major affects is that very few cities have a good public transportation system. The focus is more upon better road conditions than creating public transportation.
It also affected where people decide to live, for example, many people want to own their own home and they can be expensive in bigger cities. So people move out to smaller towns and then commute into the larger cities. This also enabled a lot of people to have bigger homes and more property than if they stayed in the bigger cities.

Answer 2

That's a very good question. The ability to travel independently and inexpensively allowed the US to develop in a different way than many countries. Besides large cities, we have suburban and rural areas which have their own industrial and commercial centers. So, American's have many choices when considering the kind of place they want to live and work.