Could Mecca be in a similar situation if something had prevented the formation of a unified Saudia Arabian?
No, I don't think so.
If the Saudis had failed to conquer Mecca and the rest of the Hijaz, then the Hijaz would have remained an independant kingdom under the Hashemites.
And politically separating Mecca from Medina and Jeddah simply wouldn't make any sense from an economic, political or religious perspective.