Tonga beat Samoa 30-15 in their opener, while Fiji sat out the opening weekend.
Canada, United States and Japan compete in Pool B with the tournament, external culminating in a final on 20 September at America First Field, Salt Lake City, Utah.
Former New Zealand back Charles Piutau, who switched allegiance to Tonga before the 2023 World Cup in France, is among Halaholo’s team-mates.
Halaholo joined Cardiff in 2016 and, after battling back from a serious knee injury, eventually left the Arms Park at the end of the 2023-24 season.
