Russia

Russia is Earth's largest country, and spans from Eastern Europe, to the Bering Sea near Japan and Alaska in the United States of America. From 1922 to 1991, it was the central country of the Soviet Union, which controlled much of Eastern Europe and Northern Asia. It is either referenced or appears in several of Toho's movies.

Mothra
Russia itself doesn't appear directly, but rather is combined with the USA to create the fictional country of Rolisica, which shares aspects of both countries. Mothra travels to Rolisica to attack New Kirk City and retrieve her twin Shobijin fairies.

The Return of Godzilla
Set in the closing years of the Cold War, the Soviet Union sends the Balashevo, piloted by Kashirin, to Tokyo to liase with the Americans and Japanese in the midst of a Nuclear Crisis. When Godzilla submerges himself (in the Japanese version), the Balashevo is damaged, causing its controls to the Soviet Nuclear Attack Satellite to become damaged, ultimately resulting in a Nuclear missile being shot at Japan. In the American dub of the film, called Godzilla 1984, the Soviets are portrayed as deliberately shooting the missile at the city, most likely to give the Americans a heroic image when they destroy the missile by shooting one of their own rockets at it.

Godzilla vs. King Ghidorah
After returning to 2204 with M11, Emmy Kano locates the body of King Ghidorah in the Sea of Okhotsk, which lies just above Japan, and is in Russian Territory.