American diver – turkey, dodo or drongo? (4)

I believe the answer is:

loon

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'american diver' is the definition.
'loon' can be an answer for 'diver' (synonyms). I'm not sure about the 'american' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for loon that I've seen before include "US bird is also a silly person?" , "Simple-minded person" , "Diver; silly person" , "Silly person (colloq.)" , "Fool" .)

I've seen this clue in The Guardian.

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