In my headcanon, Star Trek is supposed to be a reflection of our future. So, future events like the Eugenics Wars and WW3 have to be rolled forward as we ourselves move forward in time. Sort of like how continuity rolls forward in Marvel Comics or in The Simpsons (kind like how Homer was a hippy in his youth, but now has been retconned essentially into a Gen-Xer).
The way I see it now, the Eugenics Wars might have been the catalyst for WWIII, and could have happened somewhere in the 2040s or 50s. Retcons are inevitable and HAVE to happen as needed. It's absurd that Memory Alpha says the Soviet Union still exists in the 23rd and 24th centuries.
Some miscellaneous little things:
- The "supernova" that somehow wiped out the advanced spacefaring T'kon race's homeworld is of the same variety that destroyed Romulus.
- Miri's Planet was re-shaped by the Preservers as a place to plop down humanity if they needed to be uhh... preserved. Might there also be duplicates of other homeworlds such as Bajor, Vulcan, Cardassia, Qo'nos, etc.? Boggles the mind.
- The Borg are very very old, and have expanded and contracted as the eons have gone on. Seven once mentioned that their memory going back to the 15th century is fragmented. My thinking is that the Borg hive mind is limited in its expansion capabilities, and eventually reaches a critical mass, from which the Borg have to almost totally rebuild. And of course, since they're constantly bleeding off ancient memories and other data, it's nigh impossible to tell how old they are.
- And no, they have nothing to do with V'ger.
- Deflector shields, warp 7 engines, transporters, etc. took Vulcans 2500 years to perfect. Humanity only caught up because we were able to mooch off of them.
- Phase pistols and cannons are a type of laser. Phasers are what happens when you apply the phase cannon tech to a particle beam. People took to calling the things lasers cause it was catchier and got the point across better.
- Starfleet DID know about the Borg between 2152 and 2365, they just kept it Top Secret. This of course didn't do any favors for the Hansens, the Neutral Zone outposts, or the crew of the Enterprise-D.
- Romulans were once more like the way they were in TOS - noble, honorable. But those ways failed them during the Earth-Romulan Wars - the Romulan Star Empire was brought low by a bunch of upstarts, and a political revolution brought in crueler, more pragmatic leadership. Over the next couple of centuries, the state of the Romulan economy and government continued to decline, taking much of their culture along for the ride.
- Speaking of, Rrrrromulans don't have ridges.
- Andorians have 4 sexes. No, I don't know how this works.
- The delta shield has always been the insignia of Starfleet.
- MACOs are still around in the 23rd and 24th centuries, operated independently of Starfleet by Earth.
- Worf and Wesley never returned to Starfleet after they left.
- Scotty's Transwarp Beaming theory is based off of Emory Erickson's sub-quantum teleporter.
- There are seatbelts.
- Starfleet has actual military competence. This extends to training, equipment, and tactics.
- Any irreconcilable continuity errors are side effects of the Temporal Cold War.
- At some point prior to 2381, an unseen time travel incursion splits the Prime Verse into the Pocket Books and STO continuities.