I seriously doubt they are Japanese. I think there is confusion caused by the use of the name Tanuki by the American zoos as an "alternative" to Raccoon Dog.
The Zoo Atlanta ones came "from Italy" according to press articles. Zootierliste has several Italian collections with the standard Raccoon Dogs, which are readily available in Europe as an introduced species - the only Japanese Raccoon Dogs listed are at one German collection currently, and one German and one UK collection formerly.
These are not Japanese Raccoon Dogs, the US population all comes from European imports. I believe that makes these ussuriensis and it's probably impossible to know for sure.