An earlier unified Italy

It seems the fates were conspiring against Italy(Germany too, but that's for another time). A single, strong central government never arose in Italy until the 1880's.

So, what if a single government had emerged on the Italian peninsula in the 15th or 16th centuries?

Perhaps conquests by Hapsburg Spain could unify Italy, which would then be placed under the control of a separate branch of the family?

Well the problem is the Papal States, and the Spanish Hapsburgs won't help there- for example, Charles V managed to sack Rome, but he still left the Pope in charge...

Here's something to contemplate: the Papacy unites Italy.

The farther back you go, the scarier it gets. I mean, what if the Pope got his hands on the entire peninsula right when the Renaissance ends? Italians become a world power on the level of the UK and France, but under a Catholic theocracy. Now that is scary.

But I don't think it would happen.

The Anjous in Naples had a lot of power on the peninsula (some of their rulers held the signoria in various places), and Giangaleazzo Visconti of Milan had conquered a good part of Northern Italy.

Problem: The main powers (Naples, Papal states, Venice, Milan, Savoy, Florence, Genoa) were so equal in power, they could always ally against one of them which got too powerful. And even if some lucky circumstance gave one the opportunity, there are still mightier powers (Spain, Austria / HRE, France, England) who might have something against a united Italy.

A Pope-united Italy might not be so bad. Remember the Popes were oftentimes major sponsors of the Renaissance.

And assuming there aren't too many butterflies, the leftist Catholic social teachings (support for unions and such) might come around as in OTL. There might well be a nasty theocratic/Inquisitorial period for a time, but then we'd end up with some kind of religio-socialistic government.