It's just left to our own speculation. If the cracks never existed, then the Weeping Angels should have never posed a threat, the Saturnynes would never have come to Earth and Prisoner Zero would never have escaped. It makes your head hurt.
Yes, and if Amy's parents never existed than Amy would never have existed. It was made pretty clear that when something is erased from history by the cracks, its effects on history remain. That means that Amy just came into existence one day and nobody wondered where from, and the Time Lords and Daleks were destroyed at the end of the Time War, but nobody actually did it.
I was wondering why the Earth was still there for Pond to even have a wedding.
By the time of the wedding, the Doctor had flown the Pandorica into the TARDIS explosion & restored ("rebooted") the universe. That is "why the Earth was still there for Pond to even have a wedding" & it was explained very clearly in the episode -- much more clearly than things usually are explained!
After that, everything (minus the Doctor) was restored by the blast. The Doctor's presence would have been written around, especially since the time war is a fixed point. However, since Amy has a "super memory" from growing up next to the crack (EX: She can remember things partly in "The Wedding of River Song"), she was able to remember the Doctor and history corrected itself. Things should be normal, but it does leave the writers with a kinda-loophole if they need it.