If France was completely defeated, that could give Italy the opening she needed to occupy Rome and the "Roman Question" would be closed earlier, instead of becoming the open sore that it was IOTL. Possibly Italian Nationalism would not become so virulent and anticlerical, while at the same time being so powerless due to the joint Austro-French guarantee on Rome.
It is speculated the sense of "national emasculation" felt by Italian intellectuals because of not controlling the Eternal City was a major factor in allowing such a devastiting ideology as Futurism to form and eventually get to power. Maybe Marinetti would have stayed just a poet and we would still have the historical Venice instead of the modernist opprobrium(1) that was built over it and S.Peter's dome would still be standing...
It is really sad to think how he managed to hijack and pervert the labour movement in such a way.
Back to France, it is possible that the II French Empire would have collapsed immediately, instead of dragging on so long as it did: that system was deeply rotten, I think there might have been a revolution in Paris, if news came that Napoleon III had been defeated. Then what? A return of the Orleanist pretender, maybe? Or something more radical?
(1) Can you imagine still being able to cross the Canal grande on a gondola? If only it wasn't filled and turned into an alley useful only for pointless military parades!
OOC: Sorry if I went a bit overboard with this, I am open to retconning. Also will TTL have a Great war equivalent? it looks difficult without the rise of Germany, but I wouldn't discount it entirely.
Also, without the Commune of Paris the worker's/socialist movement would evolve in a very different way and this would have huge political butterflies.