It may be interesting to also consider the term "American" in the concept of uniqueley "American". The Beach Boys and Creedence have been mentioned, very american and specific to certain regions of the country. There is also the whole family of the Motown sound, Smokey Robinson, The 4 Tops, heck, even the Jackson 5. They would fall into the rock/roll definition by many. Myself, i would go for the Ramones as no. 1, Joey Ramone was truly a great american.