Robert Heinlein's World Federation,
Isaac Asimov's economy- and ecology-controlling positronic Brains,
James Blish's spaceflight-banning Bureaucratic State, Port Authority and two alternative UN governments (four scenarios here),
Poul Anderson's Solar Union and Solar Commonwealth (in his first two future histories),
Larry Niven's UN and Belt governments (in his single future history) -
- we now read about Pournelle's CoDominium of the United States and the Sovier Union.
Here are ten parallel near future regimes each preceding later historical developments. Try to fit all that into a single multiverse. Starting point: we are told that Heinlein's Rhysling and Anderson's van Rijn both visit Anderson's Old Phoenix inn - but please disregard Heinlein's The Number Of The Beast.
Pournelle's John Falkenberg is a substantial character in and of himself and in recent posts I found that, for me, he faintly echoed a couple of Anderson's characters. Onward.