Hi, and welcome to the forum.

I don't have any experience in Italy, but I live in France and I know that there, a US high school diploma is considered one year short of college admission. For admission to the first year of a French university, you normally need to have completed one year of American university or junior college.

If the Italians are saying that you need two years past a high school diploma, it sounds like they want you to have a two-year associates degree before they'll admit you to their universities.

There is information about the Italian university system on a European website called Euridyce Eurydice - Information network on education in Europe - Réseau d'information sur l'éducation en Europe
There might be something there about recognition of US high school diplomas.
Cheers,
Bev