Blum debuted internationally for Team USA at the 2006 Ivan Hlinka Memorial Tournament in the Czech Republic and Slovakia. He captured a silver medal, as the United States lost to Canada in the final. Two years later, he competed in the 2008 World Junior Championships in the Czech Republic, finishing fourth with Team USA. Set to appear in the 2009 World Junior Championships in Ottawa, Blum was named team captain of the United States. He contributed two goals and two assists in six games, but once again failed to win a medal, finishing in fifth place. He was later represented the United States at the 2018 Winter Olympics.