Assuming we're talking about a PoD around 1000.
The most obvious issue is that not only Italy was importantly divided (while it was the case of all post-Carolingian feudal Europe, Italy knew a particularly important feudal desintegration) but that it was divided under different empires : Byzantine in the south, Imperial in the north (Ottonians had direct holdings) with only Venice and southern Lombard duchies and principalities outside direct control.
(As for Sicily and Sardinia, they were respectively under Fatimid suzerainty and partial Fatimid influence).
The March of Tuscany was maybe the most "identifiable" and relativly unified feudal state in the region, but couldn't have realistically hold out against everyone (especially papacy).
The "best" attempt you could see would be the tentative of Arduin of Ivrea, but he had really little chances to stand against the full ressoruces of the Empire, with less than enthusiasts supporters.
It would require Henry II dying suddenly and conveniently, making Germany entering in some troubles...And even there, I couldn't see Arduin keeping the throne or at least not without several limitations before an increasingly divided Italy with an important numbers of German supporters among the high nobility. Even there, I'd think Italy would likely participe to the generalized troubles.