For America, of course, is inevitable (4)
I believe the answer is:
sure
I believe this is a double definition.
'for america of course' is the first definition.
(originally US way of answering 'of course')
'inevitable' is the second definition.
('sure' can be similar in meaning to 'inevitable')
'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" .)