As a nation state, Italy has emerged only in 1871. Until then the country was politically divided into a large number of independant cities, provinces and islands. The currently available evidences point out to a dominant Etruscan, Greek and Roman cultural influence on today's Italians.
I can only guess that some Irish came to Italy for the same reason that tens of thousands (?) came to the US - because of the diseased potato crops and the famine which ensued.
During the mass emigration from Italy during the century between 1876 to 1976, the U.S. was the largest single recipient of Italian immigrants in the world. However, their impact was not as great as countries like Argentina and Brazil. That was due to the fact that hundreds of thousands of immigrant...