McKenna attended Bishop Alemany High School in Mission Hills, California, where he played football, basketball, and baseball.

[12][13] He made his professional debut that year for the Tri-City ValleyCats of the Low–A New York–Penn League and was named an All-Star.

[17] McKenna did not play a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.

He was assigned to the Sugar Land Space Cowboys of the Triple-A Pacific Coast League to begin the 2022 season, but was demoted to Corpus Christi in mid-June.

[22] He played a total of 106 games between both teams, slashing .232/.337/.351 with six home runs, 51 RBI, and 16 stolen bases.

He was assigned to the Sugar Land Space Cowboys of the Triple-A Pacific Coast League on April 29, 2023.