What's interesting to note is that, in The Stolen Earth/Journey's End, the reality bomb was meant to affect EVERY universe and reality and so, surely, no matter what parallel the Doctor may be in, there should be some knowledge of its events.
Even if that logic doesn't quite add up, I don't think it is that. Instead, I think time has been distorted by this crack. Events are out of sync and out of place with each other, ever since the brief return of the Timelords (who I don't think we've seen the last of and who I think are involved in this in some way). This might be why Amy didn't know (I mean, even if TSE/JE didn't happen, wouldn't the Army of Ghosts still have happened?)
My guess is events are either being erased or distorted. They always revolve around the Doctor too, which is why I believe the Timelords are involved...