Why didn't the United States take the opportunity to dominate the world when it was the only country with atomic bombs?

Your view of the United States: Why didn't it take the chance to conquer the world when it was the only country with atomic bombs?

The actual United States: Why should I conquer the world to let those backward regions enjoy an eight-hour workday, highly mechanized agriculture, a free homeless meal with meat and drinks, and a minimum wage of $7.25 an hour? Do they deserve it?

The United States is not a charity. Once it occupies another place and turns it into American territory, it can't treat it too differently from America. Just like when California and Texas were acquired from Mexico, which now have an economic level even better than those states had when they were independent.