Yellowstone Supervolcano erupts

Explosion of Yellowstone Supervolcano, while much smaller than expected, succeeds in dismantling the United States of America. Causing power vacuum and instabilities that herald the true beginning of the Days of Fire.

The fact that Yellowstone is going to erupt soon was something that became painfully obvious by the year 2023. The growing seismic activity left no doubts. A desperate plan to defuse the ticking bomb was initiated by the US Government, with the help from a number of countries and NGOs.   The massive amounts of cold water were pumped into the carefully selected boreholes following months of detailed ground scans, researches and planning. It succeeded, but only partially. Main reservoir of overheated magma was cooled down, however it merely scaled down the disaster. Part of the magma failed to be successfully cooled-down, and the defusion attempt led to its eruption.   The result is the decimation of the Northern America. United States politically collapse. Majority of the Eastern Coast goes under emergency law, with the military de facto seizing power. Texas goes autonomous and, after a decade, independent (though it still participates in relief action. Western Coast is hit bad, with only region of California worthy of being considered a country (it receives widespread international support, which manages to stabilize it). Canada almost collapses.   The Great Plains are decimated, with big parts of them de facto uninhabited for decades. The collapse of US leaves a power vacuum (and causes a MAJOR economic earthquake).