Internationally, the Smogen, Sweden, native has represented his country at several tournaments. Most recently, Andersson registered three goals and posted a plus-two rating in seven games while representing Sweden at the 2017 IIHF World Junior Championship. He helped Sweden earn a silver medal at the 2016 IIHF World U18 Championship, as he recorded nine points (five goals, four assists) in seven contests and was selected as one of the Top Three Players on his team in the tournament. In addition, Andersson helped Sweden earn a silver medal at the 2015 Ivan Hlinka Memorial Tournament.
Andersson's father, Niklas Andersson, played parts of six seasons in the NHL (1992-93; 1995-96 - 1997-98; 1999-00 - 2000-01) with Quebec, the NY Islanders, San Jose, Nashville, and Calgary, registering 82 points (29 goals, 53 assists) in 164 career games. In addition, Lias' uncle, Mikael Andersson, played in the NHL for parts of 15 seasons (1985-86 - 1999-00) and is currently a European Scout with the Tampa Bay Lightning.