In OTL the barbarian invasions of the Western Roman Empire caused it to collapse. In this timeline the Western Roman Empire survives, though it loses a large part of its territory. The two empires work together (most of the time) and manage to survive to this day becoming some of the most powerful states in hisotry. Latin remains the most spoken language in the world and still is the official language of many European countries.
The 5th centuryBritain, Gaul, and Hispania are overrun by Franks Goths and Vandals, but unlike in OTL the Ostrogoths are defeated in Italy and they join the Visigoths in Gaul. The Vandals tried to cross the Straits of Gibraltar to get to Northern Africa from Hispania like in OTL, but a Vandal turncoat alerts the Romans and a large part of the 30 000 Vandals crossing the sea are killed when the Roman navy attacks the Vandals' improvised fleet. The Vandals are weakend signifcantly and they settle Southern Spain, and stay there, becoming allies of the Romans.
ReligionThe largest religions in the world are: Christianity, Islam, Buddhism, Taoism and Hinduism. In 1367 Christianity split in two, mostly for the same reasons as in OTL, but in 1923 AD the Western and Eastern branches managed to settle their differences and reunite. Islam has also separated into the Traditional Islam and Mongol Islam. Since the heartlands of the Hindu faith are under Christian control, Hinduism has been steadily declining since the Roman conquest of Indus in the 14th and 15th centuries AD, but ever since both Romes signed the Freedom of Religion-act Hinduism has started to regain followers.
Politics, Languages and Culture
Latin remains the most widely spoken language in the world. The Roman Republic, The United Kingdom of France and Britain, Hispano-Gallia, Baetica as well as their colonies are Latin-speaking. Although Latin has changed, the Standard Vulgar Latin (SVL) is much like Italian in OTL. SVL is based on the Northern Italian Latin dialect, and though it is not spoken as a mother tongue by the rest of the Latin-speaking world, it is easy to understand by native Latin speakers. SVL is taught in every country in the world, and 82% of the population of the world speak it. 73% of written communication on Earth is in Latin.
The (Western) Roman Republic is the largest producer of mass media; 62% of movies, TV-series, music etc. are produced in Rome and her colonies. The (Eastern) Roman Empire produces 24% of the world's mass media, being second in its second largest producer.
The World's Peace or Pax Mundii has lasted for 184 years (not taking into account unsuccesfull independence wars), The last war was the Great War when the Four Knights the Ottoman Empire, Russia, China and Japan declared war on the Eastern Roman Empire. After two weeks the Western Roman Empire declared war on the Eastern Empire's enemies, even though they had had very bad relations for a while. The war ended after 12 years in a Roman victory, though after three years of fighting The Knights were besieging Constantinople, Parisia and Carthage. The death toll of the war was 93 million people, most of whom were civilians. The Pope said after the Great War that: Had it not been for this terible war, we might have soon ended up fighting our Eastern (Roman) brothers and sisters.