Real World article
(written from a Production point of view)

According to the shooting script for Star Trek: The Motion Picture, the United States Subdivision was the Earth entity responsible for the launch of Voyager 6. This subdivision kept the response signal secret so that rival subdivisions wouldn't get data from Voyager. Centuries later, this created an obstacle for the USS Enterprise crew in responding to the ancient space probe as they didn't have the signal in their records.