I'm pretty sure the 64' GTO holds that title as the first American muscle car. You seem upset so don't get me wrong, I'm not knocking the Corvette at all (other then the mid - late 70's) as they can be very fast and are gorgeous to look at.
I have had everything from early Camaros, Chevelles, turbo Buicks and so on. Now if you want to talk about really fast cars that I have had that would have been my FED dragster and an 81 Monte Carlo. Take a look at this thread and you can see a couple
http://www.autogeekonline.net/forum/off-topic/25269-new-shop-getting-somewhere.html
I have driven everything from Corvettes, Ferraris and one Posche but my heart is in old muscle cars and drag cars.
Now back to the powder, I have seen this in a couple of Corvettes and wondered myself what the cause is. All I could think of was a poor quality plastic.