I haven't seen WATCHMEN nor read the 1980's graphic novel its based on. But I've read several reviews & some elements of WATCHMEN are the same as BTTF2 (1989).
* Both take place in an Alternate 1985.
* Both feature Richard M. Nixon still being President in 1985.
In both, isn't Vietnam still going on?
* What else is there
WATCHMEN predates BTTF2 by about 3 or 4 years. It was published in 1985 or 1986 yes? I suspect BTTF2's having Nixon still being Prez was an allusion, or salute to "Watchmen".