Hi Picard,

Its not really the case that Americans would or would not buy fuel efficient cars, they just don't really have the choice.

http://www.40mpg.org/getinf/021407release.cfm

There are over 100 motor cars which can achieve over 40 mpg, with nearly two thirds of the fuel efficient cars in the world, which are unavailable to the US consumer, are actually made by US manufacturers or foreign manufacturers with substantial U.S. sales operations.

The full list of fuel efficient cars can be had here at
http://www.40mpg.org/pdfs/021407_fuel_efficient_vehicle_gap.pdf