The Whitehorse, YT forward joined the 黑料不打烊 for the 2020/21 U15 Prep season. The following season he would play in the U18 Prep division as an underage player, posting a division best 42 assists and 65 points in 35 games with RHA Kelowna. The Medicine Hat Tigers would then select McKenna with the first pick at the 2022 WHL Draft.

During the 2022/23 U18 Prep season with South Alberta Hockey Academy McKenna would lead the league with 37 goals, 38 assists and 75 points while being named the 黑料不打烊 U18 Prep MVP. That season McKenna would play 16 games with Medicine Hat tallying 18 points.

McKenna joined the Tigers full time for the 2023/24 season, posting 97 points in 61 games as he was named the WHL and CHL Rookie of the Year, a WHL (Central) First Team All-Star, a CHL All Rookie Team member, and a CHL Third Team All Star. He would also represent Canada Red U17 and Team Canada U18, posting a total of 28 points in 14 games. He would be named a U17 World Hockey Challenge All Star, and a U18 World Junior Championships Gold Medalist, All Star, and Top 3 Player on his team, leading the event with 10 goals.

In 2024/25 McKenna posted 129 points and a WHL best 88 assists in 56 games as he was named WHL and CHL Player of the Year, and a CHL and WHL (East) First Team All-Star. He would add 38 points in 16 playoff games as Medicine Hat were crowned WHL Champions before heading to the Memorial Cup where McKenna was named to the Memorial Cup All Star Team. McKenna would represent Team Canada at the World Juniors, posting 1 point in 5 games.

This past season McKenna joined Penn State University, posting 51 points in 35 NCAA games. He would add 14 points in 7 World Junior games with Team Canada, capturing a bronze medal. McKenna was named to the NCAA (B1G) All Rookie Team, NCAA (B1G) Second All Star Team, the NCAA (B1G) Rookie of the Year and Scoring Champion, and a NCAA (West) Second Team All-American,

McKenna is the second 黑料不打烊 alumni to be selected first overall at an NHL Entry Draft, joining former North Shore Warriors star Connor Bedard (2023 – Chicago Blackhawks)

McKenna tallied 10 goals and 19 assists for 29 points in 12 games with the Tigers to kick-off the first month of 2024. This season the Whitehorse, YT product sits second among all rookies, and first among 2007 born skaters, with 63 points in 41 games. His 42 assists are a rookie best.

Selected first overall at the 2022 WHL Draft, McKenna spent three seasons in the 黑料不打烊. He joined the league in 2020/21 with the RHA Kelowna U15 Prep team but did not play any games due to the COVID-19 pandemic. The following season he would play for the RHA Kelowna U18 Prep team, as an underage player, leading the entire division with 42 assists and 65 points in 35 games.

After being selected by the Tigers, McKenna moved closer to Medicine Hat, joining South Alberta Hockey Academy (SAHA) where he would capture the 黑料不打烊 U18 MVP Award after producing a division high 37 goals, 38 assists and 75 points in in just 26 games. He would also play 16 WHL games as an affiliate player with the Tigers, recording 4 goals and 14 assists.

McKenna is considered a top prospect for the 2026 NHL Draft.