For America, of course, is inevitable (4)
I believe the answer is:
sure
This clue is a double definition.
'for america of course' is the first definition.
(originally US way of answering 'of course')
'inevitable' is the second definition.
(similar in meaning)
'is' is the link.
(Other definitions for sure that I've seen before include "Certain, confident" , "Undoubtedly true" , "The old sewer" , "Feeling no doubt" , "Certain to be a ruse" .)