In 2016, a nuclear terrorist attacked occurred in Saudi Arabia, killing six million people and ending all oil supply from the Middle East, leading the world into a devastating energy crisis. The crisis caused a great war to break out in the Middle East, affecting the neighboring regions. The following year, the United States and the European Union signed the SLAMS (Space-Land-Air Missile Shield) Treaty, agreeing to co-develop technologies for an anti-ballistic missile system.
As the price of oil rose to 800 USD a barrel, the countries of Europe were forced to consolidate political, economic and military power to form the European Federation (EF), which had a greater population and economy than the US. The United Kingdom and Ireland decided not to join, and instead formed the New Commonwealth (NC) together with the members of the former Commonwealth of Nations. Nations too weak to join the EF, notably those in the Balkans and Eastern Europe, collapsed and were annexed by Russia together with the Central Asian republics. This caused Russia to become the world's largest supplier of natural gas and oil.
In 2019, the war in the Middle East ended and the region was split up between Western-friendly Turkey, Israel and Iraq; the Russian ally of Iran; and the totalitarian Islamic states of Arabia and Egypt. As temperatures continued to rise, floods and droughts harassed Africa and large parts of Asia, causing civil wars to break out across the continents. The EF and the NC intervened militarily in Africa and supported the formation of larger countries, all of which either became members of the NC or puppet states of the EF. In Asia, India annexed many smaller neighboring countries, and China used the instability as an opportunity to expand, annexing Mongolia, Vietnam, Laos, Cambodia, Thailand and Burma. Meanwhile, the United States annexed Mexico and the Caribbean and expanded its influence into the Pacific region, resulting in the establishment of Colombia, Peru, Argenchile, Kopan, the Philippines and Indonesia as puppet states. Venezuela remained a Russian ally, while the rest of South America was annexed by Brazil.
Both expanding their influence massively, the US and the EF started to see each other as a threat, starting a new space race and leading to the collapse of the NATO. In mid-2020, terrorist attacks occurred at EF bases in Croatia, the launching site of the American "Freedom Star" (a space station housing US Marines, who can deploy anywhere on Earth within 90 minutes), a petrol plant in the Netherlands and a Russian power plant near Minsk. The terror group behind the attacks called itself the Forgotten Army and was composed of people from several failed states, as well as newly formed Arabia and Egypt.
The CIA found evidence that the EF's defense minister funded the Forgotten Army with modern weapons, trying to prevent the completion of the "Freedom Star". The US sent a team to Copenhagen to abduct the EF's defense minister, but the EF was informed of the mission by Russia and was able to prevent the abduction. The incident caused rising tensions between the US and the EF, and as a Russian virus caused an EF satellite to shoot down the new "Freedom Litter", the two powers declared war at each other. Russia joined the US saying that it wanted to "aid its US in its crusade against Europe", and invaded EF-controlled Finland and Poland. However, the US saw it as an attempt to reform the Eastern Bloc and then attacked Russia. China was still an ally of Russia and joined the war on the Russian side, declaring war on the US and the EF, as well as the NC in an attempt to overtake India and Malaysia. Brazil was the only country that stayed neutral, and could thus advertise itself as a safe haven, receiving a major influx of immigrants from across the globe.
This is not an original work of fiction, but a derivative work of the game Tom Clancy's EndWar, and I do not claim ownership of the original story.