The map shows that the unification of Italy in 1861 resulted in the formation of a new nation that included much of mainland Italy and several islands, while other areas, such as the Papal States, remained separate. Therefore, the most accurate statement based on the map is:
"The new nation included much of mainland Italy and several islands."
This reflects the geographical status of Italy post-unification in 1861 while acknowledging that not all regions were incorporated into the unified nation.