I tend to think that Nero's arrival in the past and the creation of the alternate Universe changed the past of that universe as well as the future.
The events in Enterprise are predicated on future guy contacting Archer. Nero's arrival changed the future, so future guy might not even be born in that Universe, no contact with Archer, thus the events of Enterprise change too.
FINALLY! Somebody else see's it too!
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the creation of the alternate Universe changed the past of that universe as well as the future."
Yes!
This is my own personal interpretation of it too. And it actually makes sense when you consider that in Star Trek's uni...er...multiverse, the past and the future are constantly interacting with each other (beings & ships & whatnot traveling back and forth in time) - so changes at any point in time could, and *would*, ripple both forwards *and* backwards in time!
People & events in Star Trek often interact with their own past - and have influence on how those past events play out. So if you change the future - you would change the past (and visa versa.) An event which changes the (relative) present - would change the (relative) future - and when time travel is involved it would ripple backwards and change the past too. ALL of time would...rectify...itself. (Though, of course, there aren't really consistent rules of time travel in Star Trek anyway...sometimes time travel rewrites the past & future...sometimes it creates a whole new timeline. Maybe *both* happen...in a way.)
I think that Nero's arrival *created* the new timeline - but the changes ripples backwards and forwards in time...and that explains the differences we saw on screen.
Instead of time branching off like a "Y" shape from Nero's arrival - it branched off like an "X" shape instead.
If you think about it, if that *didn't* happen - then nuSpock would have memories of a version of himself from an alternate universe journeying back and visiting him as a child (that is, if you accept "Yesteryear" as cannon, which many fans do) - and the nuTrek's history would have a crew of an *alternate* (to them) future crew of an alternate future Enterprise-E who came back and visited them. And it's 20th Century history would have Kirk & Spock & Sulu from an alternate future who visited that past twice.
I think those events - or events *like* them - may very well have happened in the new timeline - but they happened slightly differently - with *that* "new" timeline's versions of Kirk & Spock & Picard & co. going back in time (or *not*!)
Again, if you take into account that in Star Trek's universe, because of time travel, the (relative) future often interferes with and shapes the relative past - an event that creates changes in the timeline would then have a mechanism for rippling in *both* directions along the timeline.
Hence Nero's arrival creates a new timeline/history where Stardates are different, and some technology seems different from how it was in the "prime" timeline.
This is, of course, just my own personal theory - but it's how *I* choose to view the apparent differences and inconsistencies in nuTrek's universe.
It works for me. take it or leave it if you want.