The cold war was definitely inevitable. The war was about ideologies, not about actual warfare. If there hadn't been for fear of mutually assured destruction, the cold war would not even occur. However, due to the development of nuclear warfare and fear of each other, nobody actually did anything about their perceived enemy, so the cold war had to happen.
Who is to blame is debatable. On one hand, the United States intervened in foreign states without any real reason other than fear for itself, even though the countries like Korea and Vietnam just wanted to become communist countries and be let alone. The anti-soviet interventions were much more counter-productive than they were productive. On the other hand, the Soviets started getting way too much power and it was normal to oppose them, especially since they were considered to be dangerous and authoritarian. The way that they were opposed however was ethically difficult to process.
The Korean war is often called the forgotten war because it had no real impact. It lasted for a short time and when it was over everything was returned to it's prewar state. That means that the wars itself could've just as easily been avoided since nothing was changed after it. Nobody remembers it as important anymore because of everything that happened later in Vietnam.
The war in Korea was like the war in Vietnam later. Communism started rising in those countries and the United States decided to help those who opposed it. In Korea, the northerners wanted to unite the peninsula under a communist regime and the United States supported the southerners who wanted to remain capitalist. There was almost no important impact of the Korean war since everything went to its ante bellum state.
