The people fighting in Spain, Greece, and Africa were largely Italian Romans or non-Italian Romans or allies. Caesar and Pompey were Italian Romans. It was in every way a civil war of Romans. What difference does it make that, for logistical reasons, the battles took place outside of Italy proper?
> It was a handful of battles and sieges. It's nothing compared to other campaigns.
Greece was the hardest campaign of Caesar's life. For the first time, he was fighting a complete military peer that had more resources, more soldiers, and more money. Pompey even had important Gallic leaders and Caesar's #2 (Labienus) leading a much larger cavalry force. Pompey's army matched and beat Caesar's in siege warfare.
Caesar almost lost multiple times and was beaten and in retreat when he turned around to fight and win at Pharsalus. Had Pompey avoided a full scale engagement, it's very likely that he would have won.