Earth is a planet inhabited by humanity in Megas XLR. As the homeworld of the protaganist, Coop, Earth finds itself in most episodes, when not, it is mentioned, or at lease a location on it, known as Jersey City. Most of the time, aliens come to/attack Earth(mostly Jersey City) due to Coop's recklessness.
In the yester years since 3012, Earth was at peace under Earth Coalition; that was until around 3035-3037 (which Kiva is from), Earth is in a losing war against the Glorft. After Kiva failed to not only send Megas back to 3035 and get inside Megas in time due to the glorft attacked Megas' head, Megas was sended way too far into the past (was later found present Earth of 2004).
In a Alternate Universe, Earth is in ruins not because of the Glorft but due thanks to Evil Coop(who after he destoryed the Glorft for good, he went mad and cause choas across the whole universe) and Evil Kiva.