Okay, I've settled on a plague type catastrophe.
In 2014, a mysterious ancient virus is found by paleontologists in Utah and one of them takes it to New York. The Virus, known as the East Coast Plague, is a particularly sinister virus in that it's early onset symptoms are near identical to the flu. However, it's a temporary state that lasts for about 5 months before the vrus starts attacking the hosts brain, initially presenting itself in a hypomanic episode that most often actually feels like a high, until the virus begins to mature and attack the brain in a more brutal manner, escalating the mental effects into a full stage manic episode with severe delusional thoughts, paranoia, irritability and hyperactivity.
Physically, the virus causes multiple lesions that slowly grow in size and eventually develop into gangrene. Influenza like symptoms continue throughout the duration of the plague and intensify in severity as it gets worse. The disease is primarily spread through coughing.
ECP spreads quickly in New York and through New York is taken to around the world. A year later, doctors begin to notice a peculiar epidemic of people being diagnosed with an aggressive and seemingly incurable influenza and then diagnosed with Bipolar Disorder not long later. ECP is discovered and a pandemic is declared. Patients with advanced ECP are shown to be severely mentally deranged and refusing of medical help or living under qurantine, resulting in numerous ECP patients not submitting themselves to diagnosis or breaking out of containment. By 2016, ECP is declared a global health crisis with over 50,000,000 diagnosed and millions believed to be hiding it from medical practicioners. By 2017, the number of diagnosed reaches to 400,000,000 with an estimated 160,000,000 undiagnosed. Also in 2017, thousands of the earliest victims are confirmed dead due to ECP and public hysteria ensues as the death toll steadily races to 100,000 by the end of the year.
By 2018, states of emergency are declare across the world with the US, Canada, and Western Europe hit particularly hard. Riots broke out in cities with high infection rates due to ECP patients revolting treatment and paranoia of uninfected people that ECP sufferers could be lurking the streets at any time. NYC metro falls under martial law as the death toll climbs to over 5,000,000 and the world economy hits a severe recession.
2019 sees a massive spike in ECP related deaths. The world economy collapses, riots are felt around the globe. Most major cities are now under severe marital law and most countries in general have become more militarized as many uninfected citizens urge governments to utilize force against ECP patients. By 2020, the death toll now stands at over 26,000,000. An estimated 2.7 billion are now infected.
In the early 2020s, some governments allow "restless" ECP patients to be euthanized following strong public demands, driving the death toll significantly. Cure research meanwhile sees significant progress, but by 2024, the death toll has reached to over 230,000,000. It would only be by 2028 that a cure would be reached and by then the death toll was over 400,000,000, and millions wouldn't stop dying of ECP yearly until the early 2030s, which at that point the death toll had risen to over 600,000,000.
The RP starts at 2033. The plague is finally starting to be reversed, but the world has already been destroyed. Because of the nature of ECP, there are still millions of sufferers keeping the plague alive by their insistence, though most people are aware of the symptoms now and shoot to kill. It is speculated that some sufferers have developed an immunity to some of the more advanced symptoms of ECP, becoming almost zombie like madmen roaming the depopulated East Coast. But those are just rumors. Only a handful of pre-outbreak governments have survived. The rest are in various stages of disorder.
The population has been severely traumatized by ECP and the chaos that followed. Most would wish to simply try to rebuild society as it was prior, and governments are more than happy to accomodate that, but getting rid of nearly 20 years of disorder and trauma isn't so simple.
Wouldn't populations be small everywhere post-catastrophe though? But I guess they'd still be lower in previously lowly populated areas.
Though depending on the nature of the catastrophe, the smaller population over large land area could be easier or harder to maintain control of...
There's a ton of variables that would exist for that. A large but scarce nation would need more oil to move its supplies across long distances, and it'd also need more stable and reliable pre-catastrophe political infrastructure. But those viarables are too complex for a simple region RP that's probably not gonna stray beyond ten players anyway.
