However, both sides met new challenges that arose from their arrangement. The US suffered international tensions over their monopoly on Magitek and interdimensional affairs, while Mewni began a brutal civil war against a revolutionary movement. And all the while, both governments clashed over their political differences, with the US secretly funding the Mewman rebels, while the Mewman government reached out to America's rivals with magitek and intelligence.
Eventually, shortly after the US pushed the invading China from the shores of Alaska, and the Mewman government put down their resistance, the destructive capacity of man could contain itself no longer.
October 23rd, 2033 saw a global nuclear exchange that wiped out almost all human society within two hours. Witnessing this devastation, Mewni sealed away the Earth dimension, having learned the risks of meddling in the affairs of another dimension first hand.
For humanity, this marked the beginning of another bloody chapter of history. Many of those who outlasted their world did so in great underground shelters known as Vaults. When they emerged, they found that the threat of destruction had come and gone, giving way to a daily struggle for survival. And survive they did.
Eighty four years have passed since the Great War, and a descendant of one Jackie Lynn Thomas is about to emerge from Vault 13 into a world ravaged by the destruction of generations past. The trials she and her friends are about to face will not be without suffering.
Because war. War never changes.