I'm not so sure that this trend is as much as a "choice" as it is a product of the steadily-declining affluence of the USA and a very long recession that is slowly rusting into what big media desperately doesn't want anyone calling a depression.
I agree that fewer cars would be a good thing -but I don't give people that much credit more making that choice. 1 in 7 Americans are now living at or below poverty level. Perhaps they aren't getting cars like they used to because car ownership and all that it entails is slowly pricing itself out of the reach of many Americans. Forget buying a house -a car is quickly becoming out of reach as well.
America has squandered its wealth and now we are going into a period of paying for our choices of the last decade or so. Things are going to get worse before they ever get better -if they do.
Yes, a bike is a good method of transportation that doesn't tax the oil infrastructure very heavily. It's also much easier on a poverty-level budget than owning and maintaining a car -much less driving it. But I hesitate to say that people are choosing riding a bike or walking over driving just because they are making the "right choice" -perhaps it is the only choice available to many of them.