The Soviet Union was dissolved in 1991, into 15 independent republics. As Ahmadinejad said, it was just wiped out, meaning that it is no longer on a modern map. This is just what he said a few months ago about wiping Israel off the map. In both cases, he was not calling for genocide or mass deportations. The Soviet Union is no more but the Russians are exactly where they were before, now living in the independent Russian Republic.
U.S., allies conduct 20 air strikes in Syria and Iraq against ISIS, says U.S. military (Reuters)
from the article: Ahmadinejad: Israel and the U.S. would not dare attack Iran