Hmm... maybe the assassination of Archduke Franz Ferdinand wasn't comitted by a serbian Nationalist, but by an austrian Communist, alongside with an attempted coup d'etat in Vienna.
In the following chaos (civil war in Austria between Loyalist an Communist forces and maybe some national movements, german and russian Troops intervening on their respective sides), the Revolution spreads to Germany and Russia (maybe some other countries, too).
France might want to interfere, but they may have riots in their land, too, so there's no WWI but something like the

Great Red Uprising

or whatever. While Russia (with french and british help) manages to suppress the Revoution and becomes a Democracy, Germany an AH become Communist nations. Italy follows in the early 20s (just like in OTL, but here it's a communist takeover).
Still it's a little bit strange, that AH wouldn't break up, but there are two possible reasons (not that they may be realistic, I'm just trying to make som kind of patchwork-ideas here

):
1.: the "Zentralkomitte" is somehow so benevolent, that the ethnic groups don't want to leave the Austria-Hungary Union of Socialist Republics (AHUSR

)
2. (and more likely): due to heavy garrisons (maybe with additional troops from Germany and even Italy) they simply don't have any chance of uprising.
So far my first Ideas (even if they might be far-fetched I hope they're not too improbable so thas only ASBs could have make them happen)
I'm still quite inexperienced in this matter, even if it's one of my Hobbies.