Mexico
In early August 2007, Mexico coach Hugo Sánchez called-up Castillo for the three upcoming friendlies with Colombia, Panama, and Brazil. On August 22, 2007, Castillo made his debut with the Mexico national team and entered at the 53rd minute in the friendly against Colombia. In March 2008 he was also a member of the Mexico U-23 squad which participated in the 2008 CONCACAF Men Pre-Olympic Tournament in order to qualify for 2008 Summer Olympics.
He was called up by Sven-Göran Eriksson to be on the 23-man roster for the Mexico national team, but he was benched during the game against Honduras on August 20, 2008. On November 12, 2008, Castillo appeared in a friendly match against Ecuador in Phoenix, Arizona. He replaced Francisco Fonseca as Mexico beat Ecuador 2–1. He was called up for the national team again on January 28, 2009, in a friendly against Sweden. Castillo was called up to the national side for World Cup qualifiers against Costa Rica in Mexico City and Honduras in San Pedro Sula on March 28 and April 1, 2009, but was unable to travel to either match because he had "lost" his Mexico passport. [13]
United States
Under a recent change in FIFA regulations, Castillo became eligible to play for the United States. [14] The new rule allowed players of any age to make a one-time national affiliation change if they held citizenship in their new country and yet have not played in a competitive senior level match for their previous nationality. The previous rule only allowed a change if the player was under 21. [13]
On June 29, 2009, he was asked about possibly playing for the United States, saying, "I would play for the United States. I'd want to talk to them first, but I want to play for the U.S. I think it would be a very good opportunity for me, for my career. If they call me I would play for them." Castillo also said, "I have made my decision. I want to represent the country where I was born, the place where I live." [15] [16]
In September 2009, Castillo was cleared by FIFA to join the United States national team. On October 31, 2009, Castillo reveals to Mexican media after a Tigres UANL match vs Estudiantes Tecos that he had received a call earlier that day and stated "I was called up for training with the U.S. team and I am expected to appear to play against Denmark ....I'm hoping to give a good impression". [17]
Castillo made his U.S. debut as a second-half sub in a friendly against Denmark in which they lost on November 18, 2009. He then became the second player to earn caps for both Mexico and the United States, joining Martín Vásquez, who played non-FIFA-recognized matches with Mexico from 1990 to 1992 before receiving official call-ups to the U.S. starting in 1996.
Castillo's decision to join the USMNT triggered a strongly negative response from Mexican fans. "When I changed to the U.S. national team, it was a hard time for me because people called me a traitor and stuff like that," Castillo remarked. He further elaborated on his decision, ultimately stating, "It's a big priority," Castillo said of playing for the United States. "I was born in the U.S.[....] I've played a lot in Mexico because Mexico has been treating me good, I changed to the U.S. national team and I think I made a good choice." [18]
Castillo has since been recalled to the USMNT under new head coach Jurgen Klinsmann, and started against Mexico on August 10, 2011. [19]
