Question: Who became president in 2015 of the country whose ambassador to the United States from 1910 to 1919 was Rómulo Sebastián Naón? 
Sentence (from "Argentina–United States relations"): 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.
Relevant evidence: Yes