Metaphysical / Paranormal event
While some people were expecting the armageddon like scenario from the new millennium, no one expected the doomsday to be like this. In the morning of 1 January 2000, the Sun simply did not rise over the US.
The rumors of armed conflict in key cities (including Washington) did not help the situation. Before long, chaos engulfed the streets of United States. In every city, there was a different reaction: Protests against China, calls of the judgement day from religious groups and riots from opportunists. While panic spread around, government of US kept its silence.