Most foolish American, anyway! (9)
I believe the answer is:
leastwise
'anyway' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for leastwise that I've seen before include "in Hollywood at any rate" , "infrequently occurring" , "However (US)" , "If nothing else" , "anyway" .)