There is a stereotype that American cars are big and have large engines and that is quite true. But that can be said only for American cars for American market, while American cars for European market are not so big.
If you compare let's say Ford Focus and Chrysler 300 you could see a big difference. It is true that Ford Focus and Chrysler 300 are not in the same class, but they are designed with completely different philosophy, Focus is more like European cars of the same class, while Chrysler 300 is typical American, big engine, heavy duty, road cruiser. But in few past years, European market is accepting more and more of true American cars. It is not a miracle to see big American cars in streets of European cities.
The trend in modern cars industry are SUV-s (Sport Utility Vehicle). If you take a look in history of European and Japanese car manufacturers you will see that they had off-road vehicles but those vehicles were not SUV-s. Real SUV-s came from American car manufacturers, and then European and Asian car industries started to produce SUV-s, at first only for American market and later for all other markets.
American car industry is also identified by sports cars, such are Corvette, Viper, Mustang and my favorite Shelby Cobra. Those sports cars are legends in world sports cars collection.
Also true trademark of American cars are stretched luxury limousines. And in few past years there is a trend of stretched SUV-s, but that kind of cars you can't see on European roads, until for now, but everything is possible, wright?