Birnbaum debuted for the United States men's national soccer team on January 28, 2015. His first goal for the USMNT was a 90th-minute winner versus Iceland on January 31, 2016, a game in which he had already provided an equalizing assist to Michael Orozco to make it 2-2. He also played for the team in the 2016 Copa América Centenario and World Cup Qualifiers. In 2017, he played against Serbia and Jamaica.