For years, auto and energy industry watchers wondered how high the price of gas would have to climb before consumers in the U.S. — still the world’s biggest automobile market — would change their driving habits. Now they know. As the price neared and passed per gallon in the late spring and summer, American motorists cut back on their driving and started to shun the fuel-hungry small trucks and sport-utility vehicles that had been profit centers for U.S. auto manufacturers. Many even switched to mass transit, the poor step child of America’s transportation mix since the 1950s. The change in consumer attitudes about fuel efficiency has been so swift and widespread that the American vehicle manufacturers have found themselves once again behind the curve relative to their Asian and European competitors, just as they did following the oil embargo of 1973. But after the 1973 embargo and an oil price spike in the 1970s and early 1980s, the price of gasoline in the U.S. declined. Almost immediately, U.S.…