Our claim about America is extraordinary (10)
I believe the answer is:
miraculous
'extraordinary' is the definition.
(thesaurus)
'our claim about america' is the wordplay.
'about' indicates anagramming the letters.
'america' becomes 'us' (abbreviation for the United States).
'our'+'claim'='ourclaim'
'ourclaim' is an anagram of 'miraculo'.
'miraculo'+'us'='MIRACULOUS'
'is' is the link.
(Other definitions for miraculous that I've seen before include "amazing" , "Incredibly wonderful" , "supernatural achievement" .)