If all the Italian states, from Venice to Florence to the Papal state to Naples (or the Norman kingdom of Sicily), were united as one political entity some time from 1000-1500, how powerful would this united Italy be?
Instead of France, the Holy Roman Empire, and Spain dominating Italy, would Italy dominate the Mediterranean?
With the Pope being either a puppet of the king (or doge) of Italy, or the king of Italy being a puppet of the Pope, how does this affect Catholicism?