I haven't read the book you reference so I can't comment on the overall validity of the point made. Also, if your focus is on the US side of things, I think it's fair to say that the post war settlement was a failed effort to stabilize Europe - I can't say much on Wilson's Society of Natons and the reasons of tis ultimate failure.

Nonetheless, as far as your other point goes, for Italy at least I believe that focusing on the Treaty of Versailles is misleading.

First, Italy won, and gained significant portions of land - in fact almost everything they had effectively demanded. And also Italy enjoyed a fair degree of (economical) support from its allies, that made possible the continuation of the war. When Italy left the Conference in Versailles (Italy would settle its differences with Yugoslavia directly, a year later) it was as much for disagreement with the allies (the US in fact) as for internal issues.

Also, the end of the War could not be more relevant than the entire War itself; nor it had more lasting societal and political effects.

The War called to arms around 5,750,000 Italian men, causing 600,000 dead; 350,000 orphans. But that was not the end of it.

For a large swath of the population it was a mass christening to the issue of partecipation to the life of the nation: a dramatic and disruptive ritual that made them somehow aware of their collective identity. A process that found its peak perhaps in the dramatic defeat of Caporetto but took all of the four years of war, and kept going in the years after the war, connecting rising Nationalism, mass formations, socialism with the new climate of violent social struggle of the 1919-21 years (that resumed after those of 1912-13).

The sum of those experiences, all together, mattered for the Italian people much more than the loss of Dalmatia. Such effects were discussed already by contemporaries - see for example A. Serpieri's La guerra e le classi rurali italiane - and had been covered in various works later, such as P. Melograni's Storia politica della Grande Guerra.

At the same time the process of the war had various economical consequences that were entirely independent of the post war settlement - for Italy the end of the fixed axchange rate with the Allies was much more significant and worriesome, as Italy had run a staggering deficit of balance in the 1916-18 years (this threat still inspired most of the expenditure policies during the 1919-27). Also the war economy measures had strenghtened the parcellization of the Italian political institutions and the Chamber's percieved inadeuacy and corruption [see for example, L.. Einaudi's La condotta economica e gli effetti sociali della guerra]. At the same time it had forced a revolutionary change in the representative system, with 2/3 of the elected being new appointees in the 1919 political elections (one half at their first charge).

The war had also marked the beginning of mass propaganda in Italy - the first effort of this kind begun in the aftermath of Caporetto, with the insititution of a P.[ropaganda] Office for the Army. Incidentally among the most read propagand pieces were those of Benito Mussolini.

And the effects on the leadership shouldn't be forgotten either, with many of them entirely lost in the face of a catastrophe they had not seen coming - still in August 1915 the Italian Prime Minsiter A. Salandra, who had helped carry the Country into war, did not belive necessary to renew contracts for military supplies for 1916-17 nor to provide for winter clothing. These men's political decline was a result of the entire war [nor did it affect the liberal leadership alone - a few interventionists were so dismayed with the war events that suffered actual existential crisis - even threatening or committing suicide]; not merely of their failure to provide Italy with larger territorial gains. But also the prosecution of a decline that had been going since the early century.

There were in fact significant elements of continuity between the upcoming Fascist Regime and the pre war liberal state - both in terms of personal rights, state powers, legislation and balance between state powers, that made easier for the fascists to just slip into the state's boots without having to resize them.

These various continutiy elements had been discussed by R. Vivarelli - for example in Il fallimento del liberalismo but there is a long established narrative of Fascism as continuation of authoritarian tendencies within the Italian state.

I'll also steal an arrow from R. Paxton's Anatomy of Fascism in noting that authoritarian regimes rose in Europe after the war both in countries that had won and lost, sch as Italy and Germany, in neutral countries such as Spain, in countries that had begun their turn before the war such as Portugal, in countries that had lost large swaths of land - Austria and Hungary - or gained - Romania - or those that had kept fighting after the war - Grece and Bulgaria. Preexisting liberal traditions paired with a strong moderate conservative system - GB and France - appear perhaps more decisive factors in preventing the rise of fascism in its loosest definition.

The Soviet Union is a bit of a different issue - as really I wouldn't connect Stalin's rise to Versailles at all (please correct me if I am wrong).

I know I didn't go into many details but I am typing with one hand; let me know if you have follow up questions on some points and I'll try to cover them more thoroughly.