Maybe Romans lose the Social Wars. The other Italic tribes found the Federation Republic of Italia.at any point from the Marius-Sulla conflicts to Octavius beating Mark Antony, have the entire roman "empire" (referring to its large territorial possessions, not the government form) fall entirely. How can this happen?
Caesar dies in Alexandria, in the west the civil war is still going, in the east Pharnaces II is poised to take over Anatolia and (with Marc Antony tied down by the civil war and pacifying the senate) Syria probably falls to Parthia. Depending on how the civil war goes from there Rome could very well lose a lot of its provinces.at any point from the Marius-Sulla conflicts to Octavius beating Mark Antony, have the entire roman "empire" (referring to its large territorial possessions, not the government form) fall entirely. How can this happen?
It would be interesting, if the Cibri-Teutons actually settled in Italy and maintained their status as constant threat to Rome.Maybe another Cimbri-Teutoni style migration? The Romans had difficulty enough fighting off OTL's version, if they have to face a similar threat in the midst of a civil war they might not be able to pull it off.
Time the Cimbri invasion with the civil war with the social war with Mithradates doing his thing invading Greece. The problem with that is though, you'd almost insantly have some sort of deal struck with the revolting Italians, and one side is probably going to rapidly lose support in the civil war if they try and continue it (or just happen to be on the wrong side of one of those areas being invaded). From there it wouldn't be hard to sign some temporary peace with Mithradates (or even just leave him alone) while dealing with the Cimbri/Teutones.
Maybe Romans lose the Social Wars. The other Italic tribes found the Federation Republic of Italia.