What happened to North America in The Hunger Games and how might we have contributed to the destruction of it?

In the dystopian future of The Hunger Games, the continent formerly known as North America is a totalitarian dictatorship called Panem. The nation was founded after a series of wars and global ecological disasters destroyed human civilization and caused water levels to rise significantly, covering much of the land in the world. One way in which North Americans were responsible for the destruction of their own continent was participation in global wars that ultimately destroyed much of their civilization. Additionally, although the exact cause of the ecological disasters that flooded much of the earth's land is not specified, it is possible human activity caused them. Global warming, which many scientists believe is at least partially caused by humans, has resulted and will continue to result in rising water levels.