Why is everyone so surprised other countries have better gas mileage than U.S. made and destined vehicles? Japan imports all its oil, taxes the crap out of it, making a 20 mpg vehicle impractical for most people over there, not to mention taxation on engine sizes as they go ver a liter and get larger. In fact, in Tokyo, one must prove one has the space to park a vehicle before one can even purchase a vehicle there.
And Japan is not alone in what they do to encourage conservation of oil. Italy, for example, also taxes cars on engine size. As the engines get larger, the tax increases exponentially.....only the very wealthy drive these 5L and larger go-fast cars we all lust after in the U.S.
Of course, looking as gas prices in the EU should also give a clue as to the direction the various governments have taken......the average price per liter of gas there is higher than what we in the U.S. pay per gallon. We still have it cheap compared to most of the industrialized world.
But smaller cars, more expensive gas...........much comes from the fact that almost all those other mentioned countries import almost all their oil, their cities are much older and have narrower streets so our "huge" cars would have a heck of a time fitting there, and their population densities are much more biased to cities....not suburbs like here in the U.S.
Then again, most of these countries are about as large as our middling-sized states, so mass transit is much easier to put into place (kinda hard to put in a subway system that runs from Boston to, say, Orlando or Miami...but we drive those distances regularly), and our cities grew up serving cars and trucks. Most of our city and suburb expansion was after WWII, and the car really helped it along. And to drive those distances, whether between home and work or home and grandma's house three states away, Americans made a determination to have larger vehicles over 50 years ago and we haven't let go of that since.
Personally, I'd like a Mini, but the thought of driving one on the Interstate makes me think three times before I'd buy one. I know my smallish mid-sized car, that barely weighs 3K pounds, gets blown around by semis....cannot stand to think what a small car would have happen to it.....and I did drive a very small car once, a Fiat X1/9, and it absolutely sucked driving the Interstate. Was a blast in towns, but on the highway.....small cars suck so badly they provide gravity for half the earth.
We've just developed and expanded a country based on cars......our towns are spread out to no end, we drive long distances between cities for shopping, going to concerts, etc., and we've decided to not be cooped up in sardine cans while driving. That's been our decision....from before the 1950's until now, and it's not going to change any time soon. So instead we pay at the pump for the luxury of having the choice to drive something hospitable while driving.