Originally Posted by Mjolnir2000
Do they actually say in the countdown comics or the film that they haven't hopped dimensions, but merely traveled in time? If they did, then you're absolutely right. If not, then the best explanation given what we know about the star trek universe is that they not only traveled back in time, but also to a parallel reality, as we know that in every prior case of time travel within a single universe, history is actually altered and the old time line ceases to exist.
I'm not bashing the film or anything - I still plan on seeing it and I hope it's great. I'm just saying that given the info we have, an alternate universe makes the most sense.
It is described in the film as an "Alternate Reality" being created by Nero coming back in time.
There is also other dialog that talks specifically about the changes, but I won't spoil that here.