[2] He played with Team USA at the 2012 Winter Youth Olympics,[3] and he help the USA squad capture a bronze medal at the 2013 World U-17 Hockey Challenge[4] MacInnis joined the Kitchener Rangers of the Ontario Hockey League for the 2013–14 season, and was invited to take part in both the 2013 CCM/NHL Top Prospects Game[5] and the 2014 CHL/NHL Top Prospects Game.

[8] MacInnis made his first appearance in an NHL game with the Blue Jackets on December 21, 2019 against the New Jersey Devils.

[10] As a free agent from the Blue Jackets after three seasons within the organization, MacInnis signed a one-year, two-way contract to join the Buffalo Sabres on July 30, 2021.

Leaving the Sabres organization as a free agent, MacInnis went un-signed over the summer leading into the 2022–23 season.

On October 4, 2022, MacInnis agreed to his first contract abroad in signing a one-year deal with German club, Adler Mannheim of the DEL.