In 1945, The US bombing Japan twice to end WWII is pretty important. It was America's plan to finally end the war, which was a little too much. There has been a lot of controversy with the bombing still today because of the result of the bombing. So many of innocent civilians that lived in Japan died due to America's bombing, which is why there's controversy about why they had to bomb them instead of waiting Japan out. This bombing is overall important for the US because it finally ended WWII with Japan.
The Korean War during 1950-1953 was a back and forth battle between the communist countries of North Korea, China and the Soviet Union against South Korea, the United Kingdom and the US. This was an important event in the Cold War because America stepped min with the UK to stop North Korea and the Communists from taking over South Korea. If the US didn't step in North Korea would have easily taken over the South because they barely had any military force there. Overall, the war is important because the US stopped North Korea/Communism from spreading a little bit more.
The Vietnam War during 1959 through 1975 was about Northern Vietnam invading Southern Vietnam. The North actually had a military as the South did not. This caused the USA to have in get involved and attempt to help out the South. The war lasted quite a long time until unfortunately, South Vietnam and the USA fell to the North. This is still important because the US at least attempted to help South Vietnam trying to not let Communism spread there, but it was a good effort.
Soviet Union invading Afghanistan happened because they wanted to spread even more communism throughout the world. This was important because it later on caused the USA to get involved especially Reagan Doctrine. A whole lot of countries were against Communism and stopping the Soviet's from conquering more land would be helpful. It's also important because it shows that the USA would stand up against Communism and fight to get rid of it.
The Reagan Doctrine was an action of the USA invading Afghanistan supporting the anti-communist action. This was important because the USA stood up for the world and actually stopped the Soviets from keeping Afghanistan from being communist. Today Afghanistan now has terrorists and the Taliban. The USA stopped the Soviets from controlling even more power then they need, which is important
The fall of the Berlin Wall was Germany opening it ever since its closure to allow access to western countries. It was caused by the USA making a speech there about how it should be opened to the western past of Germany, since there were allied countries in that direction. But in the East of Germany, they had to build a bullet proof glass to protect the speaker, since people in the east aren't allies. This is important because it built a better relationship with the US and Germany as well as other western countries from Germany.