That would seem kind of silly as much of it is made there.
There are some US restrictions on export of equipment with strong encryption, but restrictions on import would be up to the Chinese government. Adtran might have some limitations on warranty if used outside of specified areas but otherwise I wouldn't think they would care or be in a position to prevent it.
There are companies in the business of international shipping who assist with customs issues who you might want to consult. Unlike advice here, their services aren't free, however.
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