The United States is a big country. It is looking at Brazil, another country. The U.S. government wants to check Brazil's business rules.
The U.S. leader is not happy. He has a friend in Brazil named Jair Bolsonaro. The leader thinks Brazil is not being fair to his friend.
Because of this, the U.S. is starting a check. This check is about Brazil's trade. Trade is how countries buy and sell things with each other.