They always were because that's a Jewish lie. One of the company buglers of the 7th US Cavalry was an Italian immigrant named Giovanni Martino, who is better known as "the last White man to see Custer alive" and thus named so in 1876, at the very dawn of Italian mass migration.

There was very certainly anti-Italian sentiment, in the same way there was anti-German sentiment, but it's woth noting, among other metrics, twice as many Germans as Italians were ever lynched, though on very different grounds, and Italians never had their language criminalized, whereas at least one US state (Wisconsin) expressly forbade the use of German in education.