Why is the United States becoming the strongest world power after World War II?

Even after the First World War, the United States occupied a leading position in the world. But after the Second World War, their positions have significantly strengthened. It is very easy to explain this, there was no military action on the territory of the United States, and therefore the country practically did not suffer. This allowed them to invest in weapons after the war, rather than rebuilding destroyed cities. They also gave credit to restore the devastation in Europe, thereby further strengthening their position in the world economy.