European gas prices are 8 to 10$ for a gallon. However... Unlike in the States, they have superb public transportation. For most, one car is good enough for them, and public transportation runs every few minutes to any place you need.
In the States, with exception of big cities, public transport is none-existent. We have to own a car per each person in the household! For instance, a family of 4 in NJ will need 4 cars to get around to work or college. It's a need, not a luxury. Our distances are longer as well. So do the math, at the end of a day we pay more to gas up all the cars, than our friends in Europe to gas one small diesel car even at about 9$/gallon...
Let alone the insurances premium, maintenance and whatnot. Having to pay that much for gas here would be a total disaster.