Just because the beef came form the Us doesn't mean it is allowed back in.

I used to fly a regular charter flight from Honolulu to Johnston Island. Johnston Island is a US territory but it is outside US customs. The flight originated in Honolulu and returned the same day. All catering was supplied in Honolulu. If I had an apple on the flight from JI to Honolulu, it was not allowed through customs even though the apple was put on the plane in Honolulu and never left the plane on JI. That's just how it goes.