Were Stewart O'Nan and John O'Hara of the same nationality?  
yes
John O'Hara
John Henry O'Hara (January 31, 1905 – April 11, 1970) was an American writer, best remembered as a keen observer of social status and manners in early to mid 20th century America and pre-eminent among his contemporaries at depicting social realism.
 He first earned a reputation for short stories and later became a best-selling novelist before the age of 30 with "Appointment in Samarra" and "BUtterfield 8".
Stewart O'Nan
Stewart O'Nan (born February 4, 1961) is an American novelist.
Ronaldo Vieira (footballer, born 1998)
Ronaldo Augusto Vieira Nan (born 19 July 1998) is a professional footballer who plays for Championship club Leeds United.
 Mainly operating as a central midfielder, he can also play as an attacking and defensive midfielder.
 Born in Guinea Bissau, and also holding Portuguese nationality, he is an England U20 international. Faithful (book)
Faithful is a book co-written by Stephen King and Stewart O'Nan.
 It chronicles exchanges between King and O'Nan about the Red Sox's season, beginning with an e-mail in summer 2003, and throughout the 2004 season, from Spring Training to the World Series.
 The book was dedicated to the memory of Victoria Snelgrove, an Emerson College student who was killed during the massive celebrations after the 2004 ALCS, when she was shot in the face with pepper pellets by police officers that had been improperly trained and had responded with excessive force. Dave Stewart and the Spiritual Cowboys
Dave Stewart and the Spiritual Cowboys was an English rock and pop band, formed in 1990 after frontman David A. Stewart's departure from Eurythmics.
 Chris Bostock from JoBoxers, Jonathan Perkins, Olle Romo and Nan Vernon were later joined by Martin Chambers from The Pretenders and John Turnbull from Ian Dury and The Blockheads.
 They made two albums: the self-titled "Dave Stewart and the Spiritual Cowboys" and "Honest".
 Their live stage act is characterized by spiritual icons and a unique double drum kit played by two drummers. The Rare Breed
The Rare Breed is a 1966 American western film starring James Stewart, Maureen O'Hara, Brian Keith, Juliet Mills and Ben Johnson and directed by Andrew V. McLaglen.
 Loosely based on the life of rancher Col. John William Burgess, the film follows Martha Price's (O'Hara) quest to fulfill her deceased husband's dream of introducing Hereford cattle to the American West.
 The film was one of the early major productions to be scored by John Williams, who was billed as "Johnny Williams" in the opening credits. Appointment in Samarra
Appointment In Samarra, published in 1934, is the first novel by American writer John O'Hara (1905 – 1970).
 It concerns the self-destruction and suicide of the fictional character Julian English, a wealthy car dealer who was once a member of the social elite of Gibbsville (O'Hara's fictionalized version of Pottsville, Pennsylvania).
 The book created controversy due to O'Hara's inclusion of sexual content. John and Michael Banim bibliography
This is a bibliography of the works of John Banim and Michael Banim.
 Many of their works were published pseudonymously under the name "The O'Hara Family".
 John used the name Barnes O'Hara, while Michael used the name Abel O'Hara. John Cheng
John Cheng Yeow Nam (also credited as Zhong Yao Nan; known in entertainment circle as Ah Nan or Ah Nam) (1961 – 22 January 2013) was a Singaporean actor and Getai compere who made his screen debut in "Money No Enough" and was most notable for his criminal figure roles in various media. ""
 was one of his most notable performances of a gangster figure. NAN Ranch
NAN Ranch, also known as Y Bar NAN Ranch, is a ranch in Faywood, New Mexico, that was added to the National Register of Historic Places in 1988.
 The property was developed as a ranch beginning in the late-1860s by John Brockman, who grew corn, alfalfa, and several types of fruit and bred cattle.
 Cattleman John T. McElroy purchased the ranch in 1927 and hired Trost & Trost to renovate and expand the ranch compound to become the NAN Ranch headquarters.
 The project included a new house, extensive landscaping, swimming pool, a slaughterhouse, powerhouse, and other residential and ranch buildings.
 It is historically significant due to its architecture and its role as a major 19th century ranch.