Who became president in 2015 of the country whose ambassador to the United States from 1910 to 1919 was Rómulo Sebastián Naón? 
Mauricio Macri
Title: John J. Dempsey
Passage: John Joseph Dempsey (June 22, 1879 – March 11, 1958) was a United States Representative from New Mexico who also served as the 13th Governor of New Mexico.  He was born in White Haven, Pennsylvania, where he attended grade school.  Employed as a telegrapher, he held various positions with the Brooklyn Union Elevator Company.  He was the vice president of the Brooklyn Rapid Transit Company until 1919 when he entered the oil business in Oklahoma and became vice president of the Continental Oil and Asphalt Company.  He moved to Santa Fe, New Mexico, in 1920 and was an independent oil operator and in 1928 became president of the United States Asphalt Company.
Title: Rómulo Sebastián Naón
Passage: Rómulo Sebastián Naón Peralta Martínez (1875–1941), was an Argentine lawyer, politician and Ambassador to the United States from 1910 to 1919.
Title: Argentina–United States relations
Passage: The Argentine Republic and the United States of America have maintained bilateral relations since the United States formally recognized the United Provinces of the Río de la Plata, the predecessor to Argentina, on January 27, 1823.  Since 1998, Argentina has been the only designated major non-NATO ally in Latin America, partly owing to Argentina's assistance to the United States in the Gulf War.  Relations have been strained at times over the past few years, especially during the Cristina Fernández de Kirchner administration, but they have improved somewhat since President Mauricio Macri came to power in late 2015.
Argentina–United States relations Rómulo Sebastián Naón