very interesting casting of the immigrant and native-born characters

I’ve always found it interesting how in Gangs of New York so many of the Irish characters are played by native-born Americans and so many of the native-born American characters are played by English actors.

The Irish immigrants Amsterdam Vallon, Jenny Everdeane, Johnny Siroco and Happy Jack Mulraney were played by Leonardo DiCaprio, Cameron Diaz, Henry Thomas and John C. Reilly, who are all native-born American actors. Bill the Butcher, Boss Tweed and Killoran were played by Daniel Day-Lewis, Jim Broadbent and Eddie Marsan, who are all English actors.

I have a strong feeling that that was intentional. I think the movie did that as a way of saying that immigrants to America are really Americans and native-born Americans are really immigrants.