The Western Imperium was a terrorist organization formed by members of the Ascendancy in order to carry out their goals of global reorganization. Due to a surge in White Nationalist and other rascist ideologies as a result of the formation of the North American Union and the Pan-South American Alliance, the group was named and modeled upon white supremacist ideaologies. Viewed for the most part as a large, racist gang of intrepid morons and also due to the secret influence of the Ascendancy, the organization was largely left alone by law enforcement, allowing it to operate freely. Despite being responsible for the November 29th 1993 nuclear attacks, the group managed to remain unihindered and avoided the blame until it assassinated President Vance of the NAU, taking full credit for all of its previous actitivities. Near the end of the Third World War, the Imperium seized control of the battered European Union and launched several attacks on the PSAA, which ultimately led to the Nuclear exchange which brought about the Great Collapse.
Like most of the world's societies, the Imperium was mostly destroyed by the collapse. Its remains would be mostly eradicated save for in the Northeastern United States and Western Europe, where their remaining members formed the New American Republic and the (New) Roman Empire, respectively. Both initially started as states following their ideology, but ultimately the Roman Empire would, within a generation, transform into a culturally homgenous but racially diverse post-collapse superpower whilst the New American Republic would turn into a highly backwards, hypo-rascist stronghold in the Americas.