I was scratching my head on that too. Metallica and Nirvana, but no BOC ???
(I went with the Allman Brothers)
Metallica and Nirvana are both in the Rock and Roll Hall of Fame; BOC is not. That would be one way of deciding who counts as “iconic” (albeit a controversial one; but I can’t think of any definitive criterion that wouldn’t be controversial).
I think the Beach Boys are the best band on that list, but I voted for the Doors as they are my favourite band on that list. However my favourite iconic American band is Television.