I can images Americans don't see Mercedes as sportcars. It may not look as agressive as a Honda S2000. But then again, you have speed limits which makes us laugh. I bet you could never get a Mercedes Benz to drive 150-160 mph. I think you'd consider it a sportcar then.
If you want to give it a try, come over to Holland with your Benz and we'll spend the weekend on the German autobahn. It's a nice feeling.
Sebastian.