Submissive American thanks flesh eating maniac at last (4,3)

'submissive american' is the definition.
(US term for a submissive person)

'thanks flesh eating maniac at last' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'flesh' becomes 'meat' (I have seen 'Edible flesh' mean 'meat' so perhaps 'flesh' could also mean 'meat').
'eating' means one lot of letters goes inside another.
'at last' indicates one should take the final letters.
The final letter of 'maniac' is 'c'.
'meat' placed around 'c' is 'mecat'.
'ta'+'mecat'='TAME CAT'