I'm in USA and drive a diesel
2008 Ford F-250 Super Duty Powerstroke, and a 2007 Prius.
Diesel is not hard to get, its often (but not always) on the same aisle as the gasoline pumps. It is outrageous that the best price I can find is $2.189 (70 miles from home) while gasoline is $1.659 most everywhere near.
Others pointed out that some states outlawed the sale of new diesel cars, that is not true. What those states said was all new cars had to meet the same emission standards. Diesel offerings didn't pass. Then Mercedes came along with Bluetech and broke the stalemate. California didn't change their standards, Mercedes made a diesel that met California's specifications.
My Powerstroke is of the new generation with very aggressive and active engine controls, along with a particulate filter. The exhaust smells like a propane heater, not like a traditional diesel.
My Prius gets an honest 52 MPG in daily driving but "only" 47 MPG with cruise control set at 72 MPH. The F-250 gets 8 to 18 MPG, depending on what its hauling and how fast. I calculate fuel cost for the F-250 is about 5 times per mile what I pay for the Prius, unless I am hauling a 6,000 pound camper ("caravan" to you Europeans) 70+ MPH when its 10 times the Prius.
As others have pointed out the tin cans you call cars in Europe are not available in the USA because they don't meet the crash test requirements and they don't meet the emission requirements. The new Honda meets both and should only be compared to others meeting the same specifications.