Simplify the following text for a Grade 12 native English-speaking person.
Original: The Organization of American States ( OAS , or , as it is known in the three other official languages , OEA ) is a regional international organization , headquartered in Washington , D.C. , United States .
Simplified: The Organization of American States ( OAS in English ; OEA in the other three official languages ) is an international organization based in Washington , D.C. .