American Operas, a List

1897	The Scarlet Letter	Walter Damrosch
1910	The Pipe of Desire	Frederick S. Converse
1911	Natoma	Victor Herbert
1911	Mona	Horatio Parker
1913	Cyrano de Bergerac	Walter Damrosch
1914	Madeleine	Victor Herbert
1917	The Canterbury Pilgrims	Reginald de Koven
1917	Azora	Henry Hadley
1918	Shanewis	Charles Wakefield Cadman
1919	The Legend	Joseph Breil
1920	Rip Van Winkle	Reginald de Koven
1920	Cleopatra's Night	Henry Hadley
1926	The Witch of Salem	Charles Wakefield Cadman
1927	The King's Henchman	Deems Taylor
1931	Peter Ibbetson	Deems Taylor
1933	The Emperor Jones	Louis Gruenberg
1934	Merry Mount	Howard Hanson
1934	Four Saints in Three Acts	Virgil Thomson
1935	Porgy and Bess	George Gershwin
1935	In the Pasha's Garden	John Laurence Seymour
1937	The Man without a Country	Walter Damrosch
1938	Amelia Goes to the Ball	Gian Carlo Menotti
1939	The Devil and Daniel Webster	Douglas Moore
1939	The Old Maid and the Thief	Gian Carlo Menotti
1942	Ramuntcho	Deems Taylor
1942	The Island God	Gian Carlo Menotti
1946	The Medium	Gian Carlo Menotti
1947	The Mother of us All	Virgil Thomson
1947	The Warrior	Bernard Rogers
1947	The Telephone, or L'Amour à trois	Gian Carlo Menotti
1950	The Consul	Gian Carlo Menotti
1951	Amahl and the Night Visitors	Gian Carlo Menotti
1952	Trouble in Tahiti	Leonard Bernstein
1953	The Mighty Casey	William Schuman
1953	The Taming of the Shrew	Vittorio Giannini
1954	The Tender Land	Aaron Copland
1954	The Saint of Bleeker Street	Gian Carlo Menotti
1955	The Ruby	Norman Dello Joio
1956	The Ballad of Baby Doe	Douglas Moore
1956	Susannah	Carlisle Floyd
1956	Candide	Leonard Bernstein
1956	The Unicorn, the Gorgon and the Manticore	Gian Carlo Menotti
1957	A Game of Chance	Seymour Barab
1958	Vanessa	Samuel Barber
1959	A Hand of Bridge	Samuel Barber
1961	Sweet Betsy from Pike	Mark Bucci
1963	The Last Savage	Gian Carlo Menotti
1966	Antony and Cleopatra	Samuel Barber
1976	Einstein on the Beach	Philip Glass
1977	The Women in the Garden	Vivian Fine
1979	Sweeney Todd	Stephen Sondheim
1979	The Village Singer	Stephen Paulus
1981	Satyagraha	Philip Glass
1982	The Postman Always Rings Twice	Stephen Paulus
1984	Akhnaten	Philip Glass
1987	Nixon in China	John Adams
1991	The Death of Klinghoffer	John Adams
1991	The ghosts of Versailles	John Corigliano
1991	Orphée	Philip Glass
1992	McTeague	William Elden Bolcom
1994	The Dangerous Liaisons	Conrad Susa
1995	Harvey Milk	Stewart Wallace
1996	Rent	Jonathan Larson
1998	Little Women	Mark Adamo
1998	A Streetcar Named Desire	Andre Previn
1999	A View from the Bridge	William Elden Bolcom
1999	The Great Gatsby	John Harbison
2000	Dead Man Walking	Jake Heggie
2000	El Niño	John Adams
2005	An American Tragedy	Tobias Picker
2005	Doctor Atomic	John Adams
2005	Margaret Garner	Richard Danielpour
2005	Grendel	Elliot Goldenthal
2007	Appomattox	Philip Glass
2008	The Bonesetter’s Daughter	Stewart Wallace
2009	The Letter	Paul Moravec
2010	Moby-Dick	Jake Heggie
2011	Heart of a Soldier	Christopher Theofanidis
2011	Death and the Powers	Tod Machover
2011	Two boys	Nico Muhly
2012	Dog Days	David T. Little
2013	The Perfect American	Philip Glass
2013	The Secret Garden	Nolan Gasser
2013	Dolores Claiborne	Tobias Picker
2013	The Gospel of Mary Magdalene	Mark Adamo
2014	Brokeback Mountain	Charles Wuorinen
2014	27	Ricky Ian Gordon
2014	As One	Laura Kaminsky
2014	Usher House	Gordon Getty
2015	La Ciociara	Marco Tutino
2015	Cold Mountain	Jennifer Higdon
2015	Charlie Parker's Yardbird	Daniel Schnyder
2015	Great Scott	Jake Heggie
2015	Bel Canto	Jimmy López

I'm not sure Victor Herbert counts. He was born in Germany and brought the style of German operetta to America. He was very influential here.  Menotti is our only composer to emphasize opera.  Nothing before Porgy and Bess remains in the repertoire.

I have to say this is a truly pathetic list.