What was the atmosphere like at the White House and in the US at the end of WW2 and the Cold war?

If we have to pick two key events when the US emerged as a superpower on the world map, that would be at the end of WW2 and at the end of the Cold War.

• At the end of WW2, they emerged as one of the two major superpowers in the world
• And at the end of the Cold War, they emerged as the only dominant superpower in the world, further cementing their influence.

My question is... what was the atmosphere like at the White House and across the country when these events took place? When Japan surrendered and when the USSR collapsed... When the POTUS realized that he is the most powerful man in the free world, and when an average American realized that their country was now the most powerful country in the world.