A stunning run by SA captain Celia Evans in the opening moments earned a penalty corner (PC) award and the prolific drag-flick ace Kara Stella stepped up to fire low into the net (1-0).
Evans was creating havoc for the USA defence down the left and a great intercept and pass off the right board by Jess O’Connor ultimately led to another PC and Stella nailed it with unerring accuracy (2-0).
USA captain Hannah Prince working hard to rally her team but Stella threaded the ball through to Jess Glass who put the ball past USA goalkeeper Ainslie Rhoads with deceptive ease for the girls in green and gold to lead 3-0 after just eight minutes.
A minute later and stunning build-up by SA set up another PC and Stella netted her hat-trick, but Rhian Jones equalised superbly to pull one back for the Americans shortly after for the 4-1 half-time scoreline.
The second half belonged more to the USA who signalled they will be no easy touch as the Four Nations goes into Wednesday and Thursday's round-robin matches before Friday morning's playoff medal matches.
Without taking too much away from the impressive USA fightback, it was like chalk and cheese compared to head coach Lennie Botha's team's world-class first quarter of this match.
With two minutes left it was suddenly just one goal in it as the spirited Americans struck twice in succession through a PC and then a penalty stroke by Katie Gerzabek (4-3).
USA replacement keeper Anna Zarkoski made a fine stop from a Kara Stella PC but with seconds left the Americans were awarded a controversial PC, which was overturned after umpires Emily Carroll of Australia and Karine Alves Pereira of France consulted.
Spar SA won this testing clash 4-3 and face a tough match against Australia at 8.15pm Wednesday. The 7pm match will see USA take on Namibia.
Earlier Tuesday, Australia were pushed all the way by underdogs Namibia before coming out 2-1 victors.
A Caitlin Burns deflection goal, put the Aussies in front before Ilanda Botha tipped in the equaliser, but it was Sarah Darling who scored the winner for Australia when she beat brilliant Namibia goalkeeper Petro Stoffberg just before half-time.