On December 8, 1908, a 0.4 km asteroid was spotted and was predicted to make a near miss. However, instead of in OTL, the meteor was now predicted to pass much, much closer to the Earth's atmosphere, possibly even passing through it.
On December 12, 1908, astronomers are tense. To most of the world, however, life goes on as usual. The second session of the 60th United States Congress convenes. The coronation ceremonies of the new Chinese emperor continue. The Belgian Congo enters its first months of administration.
The asteroid, 1998 WT24, entered the Earth's atmosphere at 21:29 GMT. As it fell to the earth, the meteor split into three pieces, and spread out over the surface of the planet.
The first piece impacts one km to the east of Dale City, Virginia. The District of Columbia and the surrounding area are obliterated in an instant. The United States Government is decimated.
The second piece impacts just off the coast of Durkirk, France. Northeast France is partially destroyed, and a tsunami is sent the way of Southeast England. Queen Victoria and Edward the Seventh are killed. George the Fifth, who was on a sailing trip in South Scotland at the time, becomes King of England. He does not formally assume this position until two months later, when the capital of the United Kingdom is formally relocated to Birmingham.
The third and final piece impacts in Cangzhou, China. The Chinese Monarchy, now disconnected from the rest of China proper, is relatively undamaged. However, due to the amount of damage done to the rest of Beijing, the royal family is relocated to Shenyang, where there is a large Manchu population.
The ensuing ash cloud covers the Eastern United States, Northern Europe, and East Asia. Although a majority of the world is unaffected initially, the ensuing civil unrest, succession crises, and environmental damage will change the world for the worse.