So, while it obviously is not discouraging other answers, here are some previous answers relevant to your question, which are a great read:

Did "Italians" in the early middle ages still think of themselves as Roman? by /u/bitparity

Why do we call Italians Italians? Why the name change, why aren't they called Romans? by /u/Daeres

When and why did Rome become the capital of modern Italy? by /u/alexistheman