Although these were three very different events, they all showed the reasons for one of the most important aspects of the Cold War. This aspect was the fact that the Soviet Union and the US avoided direct confrontations with one another, preferring instead to wage war by proxy if at all possible.
In the Cuban Missile Crisis, we saw why it was imperative that the two superpowers avoid direct confrontation. When the two came into such a confrontation because of the missiles in Cuba, the impact was almost completely disastrous. This showed that it was important to avoid such conflicts that could easily escalate into an all-out war.
The other two events show how this was typically done in the Cold War. In the Suez, the US and the Soviets were, to some degree, controlling their followers. The British, French, and Israelis could be seen as clients of the US and the Egyptians were Soviet clients. When the conflict seemed to be going too far, they reined their clients in. In Vietnam, the US fought on its own behalf, but only against clients of the Soviets. The Soviets did not risk getting openly involved in the war lest that lead to a crisis like the one that happened in Cuba.
Thus, all of these events reflect one important truth about the Cold War.