Do you realize that today's 'gas hog' SUVs get better milage than most of the small cars of the 1970s. We're more efficient in using fuel which only encourages more use through larger vehicles and more miles driven.
As to France or the rest of "Old Europe", look at population and number of people driving now vs in the 1970s. Their populations have not grown much nor has their vehicle use. Our population has increased by nearly a 1/3 in the last 30 years and the number of miles driven have risen in proportion to that growth.
Hogwash! Small cars in the 70s got 25+ mpg in the city and 40+ on the highways. My '75 Honda Civic, btw, weighed in at 1800 lbs and was only 150 inches long. It sported a 53 HP engine and could barely go 75 mph!
Hated the 55 speed limit - home town was Tucson and went to school in Logan, Utah - 900 miles that wasn't meant to be driven at 55. That said, some of the stuff on this thread is foolishness. The vast majority of cars get better mileage at 55 because the air resistance increases with the square of the speed. And SUVs aren't known for outstanding aerodynamics.