In my personal timeline, FC did change the timeline, producing ENT. I have a nebulous idea that in the original timeline (in my personal continuity), Captain Archer may have commanded the U.S.S. Daedelus, or some other pioneer ship, but it's nearly important enough to me to flesh out.
Anyway, FC led to ENT, which led to the Kelvin scene (in my personal continuity). I think there was too much that was different technologically and aesthetically in the movie (including that first scene) to be explained just by a 20 year divergence caused by one attack on one ship. But that's just me; I agree it doesn't matter. BillJ
said that having it all be one timeline is dramatically a more satisfying structure, and I find that to be a completely valid viewpoint. It shouldn't need to be something that holds up to anyone else's scrutiny; it just be for you whatever makes more sense and is more satisfying aesthetically or dramatically. And for me, that's the divergent timeline model.