You gotta keep in mind the infastructure of America. Travel distances are much larger than that in the UK. Cities are more spread out, and a typical work commute is usually 15-20 miles or so.
Public transportation is not as readily available, although some cities do better than others. If you live outside a major city, public transportation is almost non-existent. Things like subway systems and passenger trains may as well not even exist outside the northeast states.
Owning a car is viewed almost as a necessity of life in America. If you want a decent job, chances are you are gonna have to commute longer distances, and doing it without a car is incrediblely difficult.