Earth is the starting place in the game. It is also the main battlefield for the two factions Decepticons and Autobots to fight upon. In the Tralier and Concept art Earth is seen in ruins and destruction, probably because of the war between the Autobots and Decepticons has Ravaged Earth. It could also be because of Terrorcons a new threat in the game, or of a possible bigger unknown enemy. Furthermore Terracons are seen in some of the pictures as zombie like creatures who appear from the destruction.
Here are the locations that are fightable Locations on Earth: