the New York Dolls were punk aesthetically but musically more like the Stones. the first use of the term "heavy metal" was in a line in Born To Be Wild, but it's anyone's opinion as to whether that song is metal or hard rock. I'm sure a real metal enthusiast would not consider Steppenwolf metal. anyway who cares.
Plenty of great American bands/artists... The Byrds The Velvet Underground/Lou Reed Buffalo Springfield Television Talking Heads Moby Grape Spirit The Stooges 13th Floor Elevators Love Zappa Captain Beefheart Lots more.