HISTORICAL OVERVIEW: THE PLURALITY ARRIVAL
The date is "1987". The infection is no longer only just a biological catastrophe—it is a worldwide curse, unraveling sanity and reshaping and redefining humanity as the label of "human" is so vague at this point. The last ideals of the old world were in late stage capitalism, similar to our own, but instead of total nuclear annihilation, The Plurality and its separate parasites thrived and proved to be more effective and cruel.
The first infection came from the Elsewhere to understand the planet, quickly overtaking the world itself through its own reasoning. The cosmos was "sensing" a new planet (Earth) and sent The Plurality as a probe to view its artistry, a biological sampling hivemind, to catalog and assimilate the planet's biome. These Plurality parasites came in and took over near the 1980s, but a prototype existed on Earth far before.
The world now knows only paranoia, mistrust, and assimilation.
The main largest worry would be nuclear annihilation due to the cold war, a violent mindset for both superpowers. When The Plurality split into the world and started accidentally terrorizing the general people of both of these countries, they initially kept sections/towns/counties quarantined until they realized how much more deep the issue was and started killing people affected by it due to not being able to properly explain the issue at hand to the public.
Eventually, The Plurality found their ways into governments during the Reagan Revolution and a lot of people died because most people in charge in these sections are old and senile and quick to turn on each other. It was a very ongoing and slow regression and deterioration of the world in its existing bounds and world for the first ~5 ish years. No real form of government besides whoever has the most currency or power.
Mostly everything is the same geologically, and state lines with general culture of past states is left, this is set in what had been America/its surrounding bits. The weather is relatively the same but disasters are worse due to the lack of preparedness within the people and general lack of support and community and probably affected by infection too. Mostly the planet recalibrating itself after a sudden extinction if anything else.
The Present Day is (c. 2002-2007), yet it is still rooted in the 80s because of the lack of growth/continuity of culture other than the survival and nostalgia. Most of the old world has shut down, with life and the world attempting to rebuild itself because of faction curation and tribal thinking.
SOCIETAL STRUCTURE: POST-COLLAPSE FACTIONS
The collapse of nations fractured humanity into isolated, self-sustaining zones. Factions, gangs, and Theologians of the Infection hold sway across the land.