"Mongolia" was a part of the now non-existent U.S.S.R.

The statement is false because Mongolia was never a part of the now nonexistent USSR (Union of Soviet Socialist Republics). Although Mongolia shared a border with the USSR and had close relations with it, it was a separate country with its own political system and government. Mongolia had a socialist government similar to the USSR during the period of its existence, but it maintained its independence and was not officially incorporated into the Soviet Union.