The 1865 Revolutions were close, but ultimately France sided with Austria after the Pope fled Rome when it fell in the hands of Carlo Pisacane and he proclaimed the Comune di Roma. The socialist experiment soon fell, arguably Rome was one of the worst places in the world at the time to stage an attempt at revolution, lacking as it did any industry. In fact most of the martyrs of the "second sack of Rome" came from proto-industrialized areas in Austrian Italy, like Biella or Bergamo. The Russians sided with the rebelling Hungarians, basically guaranteeing their independence, but ghey had no interests in Italy and, like everyone, they were scared by Pisacane's radicalism.
Maybe if there had been an independent Italian State in the Center-North Italy could have been unified. I mean, if the male line of the House of Savoia hadn't been extinguished by accidents, illnesses and murders in 1807 then Sardinia-Piedmont would have been restored, instead of partitioned between France and Austria, leading to the formation of the Regno dell'Alta Italia (Königreich Oberitaliens).
You might argue that southern Italy was independent, they had also a decent army and a good navy (especially after half the Austrian navy mutined) and could have been the force behind unification, but ultimately they were too weak and their Kings were not interested at all.
Actually in 1865 they even declared war to Austria after radicals had forced a Constitution down Franceschiello's throat, but when it appeared clear that the French were not coming to help he decided to back down and, after Boniface X menaced excommunication he didn't have to arrest the Deputies, he had to save them from the urban mob, else they would have been torn to pieces...
In the end the Noth was pacified and in 1866 you had the Compromesso Storico [OOC: historical compromise, think of a better Ausgleich], thanks to the mediation of Empress Sissi (who possibly loved Italy more than Austria or Bavaria) and her friendship with Cattaneo, who had moderated a lot since 1848 and beame the first Italian Chancellor of Alta Italia. The Austro-Italian Empire (Actually The Lands and Kingdoms Represented in the Imperial Council and the Lands of the Iron Crown of Italy) was remarkably free of nationalist strife, especially after surviving the Great War and adopting the federalist and democratic constitution proposed by Hans Kelsen [OOC: sorry for the butterfly massacre].
But what if it all had failed and the Pan-Italianists had won? Italy would have had big problems: debt from the wars that would necessarily have to happen against Austria (and possibly France), lack of coal and iron for a real industrialisation and finally the task of uniting areas as different as Sicily and Friuli would have been a titanic task, for which I doubt that Italy, used to centuries of foreign domination, would have leaders with sufficient force of will and political vision.
Maybe a united Italy would have been better for the South, offering a common market for its agricultural goods, more liberal policies and capitals to finance its industries. Not being shut off from the Austro-Italian markets during the return to protectionism of the 1880's would maybe have avoided much of the emigration, and Sicily would not have become a British protectorate after the Naples' government finally grew tired of repressing the revolts there each 5-6 years...
Rome would obviously have been changed massively if it became the capital of a united Italy, it would certainly be bgger and more modern, but possibly it would have been "rationalized" losing much of its traditional character. Boniface X might have been a reactionary scarecrow, but at least he resisted the proposals by his French patrons to apply the Haussman treatment to the Eternal City!
He had to cave in on the administrative reforms however, and with French capitals the Legazione of Romagna had an industrial boom at the turn of the century. Possibly a united Italy would have been focused on the more productive areas in the Norths and in developing the big industrial centers of the South (isolated, yes, but at the time very modern) and the Center might have become less industrialised and the ideology disparagingly known as cattocomunismo might not have developed.
The Pope whithout any temporal power is difficult to imagine: I suppose he would never get to administer the Congo, right? What minor power could get it then? Or would it be partitioned?
Tuscany I don't know, probably would not be much different than today, with fierce municipal identities and an economy based on cultural tourism, high quality foodstuffs and light industry. They would probably not have the distinction of becoming the first country were a communist (well in name only, but still...) party democratically took power (in 1973), or be the first Republic associated with the A-I Empire after the last Habsburg-Lorraine Grand Duke renounced to the throne and dedicated himself to a carreer in cinema.
What colonial enterprises, if any, would this hypotethical united Italy try? Tunisia seems an obvious choice, but possibly they would decide that they need to improve their internal conditions, instead of launching into costly colonial adventures, what do you think?