Fire in the Sky
Shortly before the outbreak of the Autobot-Decepticon war nine million years ago, Starscream and his colleague and friend Skyfire were exploring an unnamed planet — the ancient Earth — when severe atmospheric conditions separated the two friends. Starscream circled the globe looking for Skyfire, but never found him.
In 1997, Unicron threatened Earth's existence, until killed by the combined forces of Cybertron. The Autobots and Decepticons continue to battle over Earth, while G.I. Joe attempts to keep Cobra from taking over the world.
This Earth is home to a variety of weird things and has a filth-ridden electronic communications system, and the people there are incredibly hostile to both Transformer factions. A massive change from the normal universes!
This world suffered a devastating Third World War in the 1980s, which among other things destroyed the Western seaboard of the United States of America and sent most of it underwater. At some unknown point in its past, there was an invasion by metal monsters from the centre of the Earth, as well as an unrelated invasion of metal monsters from space.
The United States is a fascist state in this world, commanded by President Colton, who is known for dodgy military activity. Rebel movements are at work in the country which oppose the government's infringement of personal freedoms and increasing militarism. Other foreign powers, known either to oppose the US or to be capable of pre-emptive strikes (at least in President Colton's paranoid mind), include the British, the Soviet Union, and the Ottoman Confederacy.
What If? Universes
At a pivotal point in Cybertron's history, the young Optimus Prime managed to defeat and kill the Decepticon Leader Megatron in single combat. Without a strong leader to unify them, the remaining Decepticons quickly turned on each other, breaking into small warring bands. Cybertron is relatively peaceful, and due to Autobot explorations, the planet is once again rich with Energon. However, without serious challenges, cultural stagnation has set in within the Autobots' ivory tower of Iacon. Space exploration dwindled, and the Autobots never discovered Earth.
After the conclusion of the Second World War, General Robert Savage speaks to the newly formed United Nations, and stresses the importance of not only a world diplomatic force, but a policing force. The General is placed in command of the UN's security forces, which are named G.I. Joes by the people. Joe takeover was gradual, with them slowly gathering up power. Temporary emergency powers somehow become permanent, and keep growing. Under the Joes, peace is maintained and strengthened, and even though there are still seeds of discontent, the Joes faithfully and honorably defend the principles of peace and justice. In 1982, Joe science teams uncovered an alien spacecraft and studied it, which gave them a huge technological edge. They use this edge to enforce their will across the world.