Most Influential American Musician of All Time?

Miles Davis, Robert Johnson, Duke Ellington, Louis Armstrong, Irving Berlin, George Gerswin, and Elvis Presley, in no particular order.

The question itself is subjective, and therefore has to definitive answer.

Cheers,
John

Elvis was a very good singer, a poor to fair guitarist, barely a songwriter, and a mediocre (benefit of the doubt on this one) actor.

He was a great entertainer but hardly a musician.

I agree that the question of who is the most influential is subjective and, therefore, has no definitive answer. But I think this question is far less subjective than "who is the greatest."

Although I had initially suggested Louis Armstrong, and still feel that he is right up there, subsequent posts have me thinking more about Robert Johnson and Bob Dylan. All three of these musicians seem to have influence that goes way beyond their own musical genres. Can the same be said of, for example, Gershwin, Berlin, or Grandmaster Flash?

Frank Zappa, Leonard Bernstein, Robert Zimmerman, Miles Davis and Frank Sinatra

Can I have an example of someone (who in their own right have made a significant contribution to American Music) who's been influenced by Frank Zappa?