User blog comment:JERealize/What lies beyond Panem?/@comment-2.30.34.194-20130717165954

My guess is that after world war 3, the world was divided. Some parts became uninhabited while others became more so. Due to WWIII the human race was majorly depleted and surviviors grouped into places that were safe, creating nations like Panem. However very few nations of anothers existence and Snow created a unbreakable barrier around Panem. Therefore the Hunger Games were unnoticed by any other nations.