What does USSR mean in REGIONAL

The Union of Soviet Socialist Republics (USSR) was a socialist state that existed from 1922 to 1991. It was the first and largest communist state in the world and was one of the most powerful countries of the 20th century. The USSR covered an area of more than 8.6 million square kilometers, spanning eleven time zones and encompassing more than 15 ethnic republics. Its people shared a common language, socialist political ideology, and, most importantly, a common identity as citizens of the Soviet Union. At its peak, the USSR had over 270 million citizens making it one of the largest countries in terms of population at the time.