I've just finished reading Without Warning, an action thriller by the author of the alternate history/future series Axis of Time. Birmingham wrote Without Warning after he heard an anti-war protester assert that the world would be a better place without America. In the novel, the protester gets his wish.
In February 2003, A strange energy force hits the earth, consuming almost the entire continental United States, as well as much of Canada, Mexico, and Cuba. It kills all life inside of it. America now consists entirely of Alaska, Hawaii, the northwestern corner of Washington State, and US military forces and citizens abroad. The world promptly goes to hell in a handbasket, suffering a global financial collapse as US capital and demand for goods has literally vanished. Worse, with the sudden absence of American "political ballast", political unrest ferments across the globe, leading to wars, both conventional and nuclear.
Without Warning is a fast-paced thrill ride. I highly recommend it.