Who caused the Cold War?
The Cold War emerged out of mutual distrust on both sides. In 1945, the Soviet Union now stood on military parity with the Western Allies as well as holding most of eastern Europe. The United States feared a potential Communist invasion into the West and Stalin feared the West invading the USSR as Hitler had done. The US using Atomic bombs at Hiroshima and Nagasaki are seen by some as the first volley in the Cold War while others see the emergence of the Iron Curtain by the new Warsaw Pact as the beginning. But both sides feared another war so soon after the end of the most costly war to date and wanted to curb any potential conflict however they could.
Cold war was a war of threats, politics between democratic west and communist east. It was caused by the end of WWII with the emergence of two super powers America and the USSR, and their opposing ideologies. It was called a cold war because there were no occasions of direct armed conflict between the super powers.
What was specifically happening in the world the caused the cold war to continue and how did it continue for over forty years?
The cold war caused the Vietnam War. The Atom Bomb created the cold war. If there had been no atomic bombs, there would have been no cold war. If there had been no cold war, the US may not have been involved in Vietnam in the first place. If the US had been involved, the US would have declared (total) war and defeated North Vietnam just like the US (allies) defeated Japan/Germany in WW2.
It wasn't POST WW2 that contributed to the cold war. It was the nuclear weapon itself that caused the cold war. Without the atomic bomb, there would've been NO Cold War. Cold War means a stand-off between two enemies. If no super weapon exists (Atomic Weapons) then there's NO stand-off...they fight instead. Just like in the pre-atomic past.