The most common and most likely answer to this crossword clue is the 8 letter word NEIGHBOR
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Buddy explains!

The straight part
We know that "In the U.S., be next to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in the u.s., be next to = neighbor.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 NEIGHBOR mean?
NEIGHBOR noun- A person living on adjacent or nearby land; a person situated adjacently or nearby; anything (of the same type of thing as the subject) in an adjacent or nearby position.
- One who is near in sympathy or confidence.
- A fellow human being.
- To be adjacent to
- (followed by "on"; figurative) To be similar to, to be almost the same as.
- To associate intimately with; to be close to.