How is the president of the united states considered the most powerful person on earth and where does this pow?

The United States is considered the most powerful country on earth so I ume the president of the most powerful country would be considered the most powerful man on earth. Edit: The person above me is wrong, the US is definetly not the wealthiest, we are trillions of dollars in debt to other countries. Also, I highly doubt that polaticians and citizens of other countries consider our president the most powerful man on earth, they usually dislike our president and the US getting so involved.