Seems to me that the Temporal shenanigans in Enterprise would have caused considerable changes to the timeline, and that is on top of the alterations caused by First Contact.
Off the top of my head, the Klingons were encountered early ( though it would appear that contact would have been made by 2154 anyway). A different Doctor was assigned to the Enterprise ( with potentially grave repercussions for at least one species). Arguably T'pol would not have been part of the crew.
And those are fairly cosmetic changes, the Suliban were advanced by a future agent, and Enterprise got its hands on some of that technology. The Earth was attacked by the Xindi, and Enterprise entered the expanse, gaining knowledge of Tech it would not have hitherto seen. Its almost certain this would have made Earth a bit more militaristic which would alter ship design and uniforms etc.
Additionally, since Trek shows a number of stable timeloops, its entirely possible that THOSE are affected meaning that Nero's arrival itself could impact on events prior to 2233 ( wibbly,wobbly, timey,wimey you might say
So in summation, no everything was not necessarily the same before the Kelvins destruction, but that does not necessarily mean it is not the prime universe.