How did regional differences in Italy initially prevent unity in the new nation?

The regional differences in Italy influenced different popular principles that held by people in each regions

For example, at that time several religions in Italy disagree on how Italy should treat their relation with other European countries.

Some people believe that those other European countries were once belonged to the Roman empire. So they need to re-claim those nations. While the other believe that they should forget those and focused on maintaining their current territory.

This difference caused so much conflict in Italy which prevent the united to be formed in the new nation.