Which political organization was most associated with the iron curtain countries?

Warsaw Pact, is the right answer.

Explanation:

Following the end of the Second World War, the Soviet Union erected a military, political and ideological barrier to seal off itself and its dependent allies from eastern and central Europe from public contact with the West and other non-communist states is known as the Iron Curtain. Though the term Iron Curtain was used throughout history in different contexts, Winston Churchill was the first to use this term to describe the policy of Soviet Union for blocking itself and its satellite countries from public association with the West and its allied nations.

In this way, the Eastern Bloc of Europe has been referred to as the Iron Curtain or Warsaw Pact.