Do Italian Catholics eat a traditional St. Paddy's Day supper?
Italian American Catholics?
Pretty much anywhere in the USA where there is a large contingent of both Irish/Americans and Italian/Americans, you will often see (though muted over time) a certain rivalry of the two ethnic groups.
Italian-Americans often made a point of wearing red on St Paddy's day to show everyone that the were NOT Irish.
And as far as feasting is concerned, I don't think a single self-respecting Italian American would dare consider Corned Beef & Cabbage to be a "feast".
Italian-Americans will often also make a point of celebrating St. Joseph's day (patron saint of Sicily) on March 19.
If it falls on a Friday, they don't give a shit, because Italians cook fish/seafood with aplomb--no damned fish-sticks for them.
In Italy itself, I doubt St Patrick's day is all that big a deal--they have other Saint's days to feast on-, and in Ireland, corned Beef and cabbage is NOT a traditional St Paddy's day meal at all.