Back when I was working on my dissertation for my PhD in history, I read a lot of primary sources and secondary sources from mid 20th century US foreign policy and other government figures. I was reading old memoirs and diaries and papers and notes 8 hours a day.
At some point it became crystal clear that the history of the Cold War was not what I had growing up. Yes, there was a threat of worldwide communist takeover and Stalin was directing operatives around the world to further his goals, but that was not it.
Truman became president without knowing much at all. I am not a big fan. He was the front man for the Kansas City machine. He wasn't very bright. It has come out more recently that he greatly profited as president, contrary to his lies. FDR thought little of him and kept him in the dark.
Once FDR died, Truman was surrounded by FDR's men. Because FDR kept many things close to himself and didn't involve the wider government in policy making, many of these FDR men really had not been involved in formulating policy and didn't know FDR's intentions. But with the new president, they moved right in and pushed Truman into their policies.
The main fear of Truman and his administration wasn't communism, but returning to an economic crisis. They knew that WW2 had been responsible for getting America out of the Great Depression more than the New Deal programs. They knew Americans were weary after sacrificing for the war effort. They knew that Americans wanted to pull back from international engagement, just like after WW1.
Their fears of a renewed economic crisis were the central diving force in their thoughts and actions. They knew they needed an enemy to keep Americans engaged internationally and to justify continued military expenditures and high taxes.
Even if the Soviet Union had been ultra cooperative after WW2, it still would have been demonized in order to keep Americans involved. And we can see this method continuing today.
When the Cold War ended, America floundered for a bit. Bush had Gulf War I, which is starting to look more and more like an unnecessary war of choice and the beginning of the pivot to a new enemy. Clinton intervened in the former Yugoslavia and wagged the dog against Bin Laden with cruise missiles.
But then 9/11 happened and suddenly we had all this money for two massive wars and occupations. We had a great enemy, Islamic extremists(but remember, not all Muslims are terrorists and Islam is a “religion of peace”.
And when this finally played out, we have a new enemy, Putin, the alleged most evil man since Hitler. Oh, they got their target. Regular Americans express strong emotions about Putin. It is like magic. So many otherwise reasonable people get twisted up over a conflict on the other side of the world.
So, back to the original question, the answer of who is responsible for Cold War is America and Harry Truman. He might have been pushed by advisors, but he adopted the policies. And we paid the cost.
America doesn't need constant enemies to keep the economy moving. The mindset needs to disappear.
I'm no Truman fan, and he clearly was in over his head as pretty much all Vice Presidents would be, however, it is a bit unfair to lay the primary blame for the Cold War at his feet. Although impossible, you would have to find the alternative person that would have done something drastically different than he did. I think you'd be hard pressed to come up with who that would be and what they would have done. (And argue it would have resulted in a better result) It might be more fair to think of Truman in the context of what Eisenhower's policies were and how he handled things. He was far smarter, and realized that we had both a real, existential external enemy in the Soviet Union's totalitarian ideology, and how that would lead to his warning about the unfortunate necessity of the military-industrial complex (the Devil we know?) that has been ruling us ever since (and has now, ironically been taken over by the very Communists it was created to fight). It was (and is) legitimate for Truman and his advisors to believe that the nation's economic health would be so important in the context of an enemy (would that our current leaders would recognize the fact as well...). Recognizing that our economic weakness (contrasted with of the vast improvement in the German economy under Hitler, most notably touted vociferously as "the future" by Joe Kennedy) made Hitler's war easier for him to justify to his people, and made it harder for FDR to justify the US getting involved at all. Thus our economic weakness, it could be argued, led to a worse outcome than if we were economically strong enough (and not so domestically distracted by the Depression) to push effectively back on Hitler's ambitions. I think that is a better context in which to consider Truman's policies and their effect on whether he is "responsible" for the Cold War. After all, the Soviet Union/Stalin didn't really HAVE to consider the US an existential enemy. They didn't HAVE to subjugate both domestic and foreign enemies and start wars of conquest (except to the extent that the imposition of ideological Marxism basically requires it). I lay the blame solely on Stalin. Almost everything we did was a reaction to him, especially once he got nukes. One must know whom considers oneself an enemy and act accordingly, after all. Truman was a dope and dupe. But we've had (have) much worse...