The most common and most likely answer to this crossword clue is the 9 letter word UNEQUALED
U
N
E
Q
U
A
L
E
D
Buddy explains!

The straight part
We know that "Unique /in the U.S." is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unique /in the u.s. = unequaled.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does UNEQUALED mean?
UNEQUALED adjective- Unmatched, superlative, the best ever done, record setting.