The title says it all; what is the latest POD you could imagine that could lead to a World State by 2000 AD. This state can be of any kind, an Empire subjugating all, a Confederation of member states, a unitary or Federal democracy...
Fantasize away!
EDIT: Posted in the pre 1900 forum because I'd imagine most PODs will be there... but feel free with plausible post 1900 PODs too if you can imagine any.