In July 2019, he signed a homegrown player deal with the senior side, effective from the start of the 2020 season. His first-team debut with Atlanta United arrived on March 7, 2020, with George coming on late in the first period as his team defeated FC Cincinnati 2-1. 

Campbell played plenty of football in 2021, appearing in MLS, CONCACAF Champions League and USL Championship matches for the first and second teams. He scored his maiden goal in September of that year, notching the first in a 3-0 win over an Orlando City side which had Baggies forward Daryl Dike in it. 

George added 21 further first-team appearances to his tally the following term, but ended 2022 by signing a three-year deal for CF Montréal on December 13.

The defender played 29 times for his new team in 2023, making his debut in a 2-0 home triumph over New York Red Bulls in April. Campbell’s first goal for the Canadian club came in dramatic circumstances, bagging a late, late winner in a 1-0 home victory against New England Revolution in August.