First, I agree that driving fun, a very subjective concept to be sure, is the most important thing in a car. If it's not fun to drive, take a bus or train to where you are going. That's why I prefer pre-1980 British sports cars, I find them the most fun to drive.
However, before making generalizations about American cars not being fun, consider the Shelby Cobra, any of the Allard variants, the Vector W8, most of the Corvette line, the Saleen, and the Ford GT/GT40, just for a few examples.