[3] For the 2013–14 season, Forsbacka Karlsson moved to North America to play with the Omaha Lancers of the United States Hockey League (USHL).

[5] He was selected to participate in the 2014 CCM/USA Hockey All-American Prospects Game[6] where he was named his team's the most valuable player.

Forsbacka Karlsson committed to play the 2015–16 season with Boston University,[7] and following the 2016–17 Terriers' run for the 2017 NCAA Division I Men's Ice Hockey Tournament, as announced on 2 April 2017, Forsbacka Karlsson signed a three-year, entry-level contract with the Boston Bruins.

As an impending restricted free agent, and with the Bruins in the midst of their playoff run to the 2019 Stanley Cup Finals, Forsbacka Karlsson opted to pause his NHL career and return to Sweden after six years, citing family reasons.

[10] Forsbacka Karlsson helped Swedish team win the gold medal at the 2013 World U-17 Hockey Challenge.