Not treated properly, when sleeping round America (6)
I believe the answer is:
abused
'not treated properly' is the definition.
(to abuse is to mistreat)
'sleeping round america' is the wordplay.
'sleeping' becomes 'abed' (I've seen this before).
'round' means one lot of letters goes inside another.
'america' becomes 'US' (United States).
'abed' enclosing 'us' is 'ABUSED'.
'when' is the link.
(Other definitions for abused that I've seen before include "vilified" , "Reviled or exploited" , "Swore at" , "Insulted; violated" , "Uttered insults, attacked in words" .)