Born in Aberdeen, defender Souttar changed his allegiance to his mother's homeland earlier this year and enjoyed a first appearance to savour at GIO Stadium in Canberra.
The Fleetwood Town centre-back repaid Graham Arnold's faith with a headed double after a pair of early finishes from Maclaren, who completed the scoring and his treble in the closing moments.
Australia's apparent reluctance to overexert itself meant the expected avalanche of goals never truly arrived, though the Socceroos did move top of Group B.
Kiran Chemjong's failure to grasp a Craig Goodwin shot gifted Maclaren the sixth-minute opener and the striker quickly doubled his tally, heading home after Rhyan Grant nodded Aziz Behich's cross back into the danger zone.
The towering Souttar was proving a nuisance at set-pieces and managed to stoop to meet Goodwin's corner for Australia's third in the 23rd minute.
A fourth would have followed on the stroke of half-time if not for the match officials, who disallowed a deflected Mathew Leckie effort for offside despite Ananta Tamang being responsible for the touch that deceived goalkeeper Chemjong.
There was no denying Souttar a double, though, as his 59th-minute header from Aaron Mooy's cross dribbled in off Dinesh Rajbanshi.
Arnold turned to his bench after the hour but no other Australian was able to add their name to the scoresheet against the world's 161st-ranked nation, leaving Maclaren to claim the matchball as he fired home in the 90th minute following Jackson Irvine's cushioned control.