Russia was mainly responsible for this event because Stalin initiated the conflict with the blockade and threatened to let thousands starve. The US only reacted to the situation that Russia created, which ultimately saved the people of West Berlin.  

Although both the US and the USSR played major roles in the war, the USSR played a slightly more significant one because they aided North Korea in the initial charge to conquer the country, in an attempt to spread communist influence. After the initial charge, the support the US gave the South and the USSR gave the North were roughly equal.

The Marshall Plan was an United States foreign policy introduced in response to the growing possibility of a Communist controlled western Europe. Though the Soviet influence created fear and doubt in Americans' minds, the Marshall Plan was created by the United States to help western democracies. Soviet Union has no direct contribution to such a decision, therefore shares rather minimum blame. 

The Truman Doctrine was the embodiment of the containment policy in response to the two threats: a communist-led uprising against the government in Greece and Soviet demands for some control of a water route in Turkey. Although the Doctrine was created due to Soviet influence, the decision was made by President Truman and supported by Congress, thus making the United States far more responsible. 

The Chinese Revolution and the Chinese Civil War was an important event in the period of Cold War as the Chinese government was backed by the Soviet Union. The signing of the Sino-Soviet pact seemed to provide further proof of a worldwide Communist conspiracy which alarmed the United States. Although the communists were closely tied with the Soviet Union, General Marshall stated that he knew of no evidence that the Chinese communists were being supplied by the Soviet Union. This means that the massive military support provided by the United States to Chiang's Nationalist government had a rather significant influence of the war. Since the Soviet Union had little influence on the war, the United States, the Communists and the Nationalists from China should split the blame. The economic and historic background of China gave rise to the communists while the Nationalist government was incredibly corrupt. Since the United States had very limited options regarding riding China of Communist influence, it only shares 20% of the blame as the rest contributes to China and its people. 

Dropping the atomic bomb was a decision made entirely by the United States government, mostly by President Harry Truman. The Soviet Union played little to no influence in such a decision as the bombs were mainly used to force a surrender from Japan. Although threatening the Soviet Union and display America's military strength may have been an motive, the Soviet Union shares no blame in the dropping of the bombs and the United States is solely responsible.

The Potsdam Conference had arguably less significance compared to the Yalta Conference as fewer agreements were made. However, 
similar to the Yalta Conference, the Potsdam Conference was peaceful as the leaders discussed post-war possibilities of the world. This had no direct relationship with the signature arm race of the Cold War and neither side bears blame.

The Yalta Conference occurred before Germany and Japan's surrender and therefore was rather peaceful as the three leaders tried to reach consensus. The agreement made at the conference is rather fair and peaceful with an emphasizes on new world peace and self determination. Since this was a peaceful and successful conference, the Soviet Union and the United States bear no "blame" and were equally responsible for the outcome of the conference.

The responsibility for this event falls equally on the US and the USSR, as they both competed to create the same thing. The discovery of the possibility of the hydrogen bomb was discovered by both countries at around the same time, and were pretty much neck-and -neck throughout the whole development of the bomb.

The United States were mainly responsible for this because the USSR did not actually do anything during this event. The CIA acted based on their fears of what the USSR could do, not what the USSR actually did. A combination of paranoia and greed led the US to conduct operations in Iran. However, Soviet influence was spreading to other countries at the time, so they influenced the event a little.

The United States was mainly responsible, as they sent a spy plane out without any good reason to. It was completely reasonable for the USSR to cancel the agreement, as it was an infringement on its values right before it was put into place; it created a bad impression onto America. It was a reckless decision by the US government that was directly responsible for the cancellation of the agreement.

The USSR held the main responsibility for this event, with the United States having a small role in it. The Warsaw Pact was an agreement in direct response to the creation of the NATO. The NATO, which was partly created by the US, was the inspiration for the Warsaw Pact; However, it was the USSR's decision to create an alliance, giving them the main responsibility for this event.