Ok, regarding Italy that's more or less the part that i know better:
- No Caporetto mean...a lot, it was a defining moment for Italy, terrible loss and the need to basically rebuilt the army, Veneto devastated and looted; here is not necessary and so a lot of saved lifes and money; the fifth national loan will be probably butterflyed away due the lack of necessity to replenish all the equipment lost in the OTL battle.
https://en.wikipedia.org/wiki/Battle_of_Caporetto here for a quick show of the italian loss but i suggest the italian one and use google translate as it's more accurate.
That has also political consequences, both internal and external; for the first, well the Boselli goverment will not fall and Vittorio Emanuele Orlando will not take his place...still Boselli is 80 years old and it's more probable that will leave the political initiative at the peace conference to Sonnino the foreign minister that's an hardliner and will ask the full implementation of the London Treaty.
For the second, well no need to send british or french division in Italy (for a short time) to prop up the italian army and the italians basically conquered what assigned by the treaty already and alone, while Serbia is still fully occupied...and this mean more political clout at the conference
- Wilson mediation, well ITTL the american president have less direct influence and prestige at the conference as american expeditionary corps is just begun his deployment in Europe and his number are very low; not that this will stop him to be the usual dick but he will have less clout than OTL...even because the europeans are slighty better and ITTL he will also need to deal with Russia and this mean less time to concede at the Adriatic question and more stress for him and his not excellent health.
Also with Russia not nullify the French loan the general economic situation of France and the continent will be slightly better, eroding a little bit more USA capacity to influence
- Italy takeover by the fascist was always a very complicated thing and dependent from a lot of different event; no communist revolution in Russia with his fallout over the world mean less general fear of a revolution in Italy and the slightly better economic situation also mean more stability.
There will be violence and riots? Sure but Benny rise is hardly a given in this situation.