This is going to be another crazy one, but bare with me as always.
I have a fan theory that connects two completely unrelated movies: The Hunger Games franchise and the Jim Carrey movie, The Truman Show.
I believe that the place in the Truman Show where Truman lives, is also the arena in The Hunger Games. You may say that is stupid but think about it, they are both domes, they both have hidden cameras, they both can change the weather and environment in side the dome, and they both were used to brodcast and film television programs.
My theory is that the outcome of the Truman Show could also have caused the series of events that made Panem come into existence. The Truman Show was a big deal all over the world in the movie. What if it's end prompted like a war or something that made America somehow become Panem. And after words they used the Truman Show filming site as the arena for the Hunger Games after the Rebellion.
Let me know what you think in the comments.