Tomasin debuted for the U.S. national rugby team as a teenager at the 2013 Gold Coast Sevens.[4] He represented the U.S. national team at the 2015 Pan American Games.[4] He suffered a setback in the fall of 2015, however, when he tore his ACL, and as a result he was out for several months. At 21 years old, Tomasin was the youngest of the 26 U.S. rugby players vying for a place on the U.S. 12-man roster for the 2016 Summer Olympics,[1] but he missed out on national team selection.
Tomasin returned to the squad for the 2016-17 Sevens Series.[5] He scored eight tries at the 2017 Singapore Sevens, and was one of three U.S. players to make the seven-man dream team.
Tomasin returned for the 2017–18 Sevens Series, but was injured and missed several tournaments. Tomasin played some spells at halfback, instead of his usual forward position, due to injuries to scrum-half Madison Hughes and utility back Maka Unufe. Tomasin had an excellent 2018–19 Series; he played in every match en route to the U.S. best ever second-place finish, and finished as one of the three U.S. players selected for the Dream Team composed of the seven best players.
