Why didn't Austria-Hungary back down to the british ultimatum in 1914?

[Kyriakos]

Serbia would also need a very public bone to be throne their way, as for the French the war was prosecuted in their "defense" and among the surviving Allied powers they had "suffered" the most. Further, a collection of strong regional powers was key to France's future strategy of containing the successors to the Hohenzollern & Habsburg states.

In the minds of the Allies, Italy should content themselves with bits of Austria proper, and if not they can suck an egg...

Italy's part in ww1 was pretty much against the entente anyway, given they even lost lands and had to be helped by entente troops to keep the border and avoid revolt. So they couldn't ask for anything after such a failed show.
That said, look at what Romania got (which pretty soon got it into major trouble with Russia, though).

 

[Gen.Mannerheim]

Italy's part in ww1 was pretty much against the entente anyway, given they even lost lands and had to be helped by entente troops to keep the border and avoid revolt. So they couldn't ask for anything after such a failed show.
That said, look at what Romania got (which pretty soon got it into major trouble with Russia, though).

The Romanians had a very clear cut reward (Siebenbürgen/Transylvania) for joining the Allies and had actually surrendered to the Central Powers in 1917, which precluded them from getting anything more even after they reentered the war in the closing days. Though what more that they could have gotten is unknown.

 

[historix69]

The Romanians probably simply profited from self-determination.

see the map

Spoiler :