Spaghetti, cheeses, oils, and tomato products that Italian immigrants were familiar with were considered “high end” back in Italy. Poorer laborers in Italy would have associated these foods and meats with holy days. When they immigrated, they preferred the better quality food they remembered to what other immigrants and laborers were eating.
The first Italian restaurants in the U.S. started out basically as additions to boarding houses for single Italian men. Over time, the restaurants began to cater to Italian families and occasionally non-Italians came by. Italian restaurants didn’t intentionally cater to non-Italians until after the 1920s.
Source: Diner, Hasia R. Hungering for America: Italian, Irish, and Jewish Foodways in the Age of Migration. Cambridge, Mass.; London: Harvard University Press, 2001.
Follow up: Was French cuisine always regarded as high class and served in fancy restaurants, even during the British colonial period? If not, when did it start?
Something this thread hasn't touched on is the economic status of Italian immigrants in America. In the 19th century, Italian food was highly regarded by parts of America, most notably Thomas Jefferson. However, in "The Ethnic Restaurateur," Krishnendu Ray writes -
"Italian food would be dislodged by the entry of new southern Italian immigrants between 1880 and 1924 who were numerous and mostly poor, hence derided by the taste-making elite...When American Italians climbed out of the ghetto and into sports arenas, corporate offices, governor’s mansions, city halls, and movie studios, Italian food was re-assessed in the American imagination"
Based on the quote above, it would seem that we valorize French cuisine in part because there has never been a large wave of poor French immigration, and other ethnic cuisines rise in fall in public perception based on our collective valuation of their culture. Another example of a cuisine that has risen in perception is Japanese food.
Jefferson on Macaroni: https://www.monticello.org/site/research-and-collections/macaroni
The Ethnic Restaurateur: https://www.amazon.com/Ethnic-Restaurateur-Krishnendu-Ray/dp/0857858351
So many great responses! Thank you so much!