All aged under 23, the quartet was anchored by Hayden Wilde who burst away from 2016 Rio Olympian Gordon Benson on the run to win by 9sec, with the USA third and the Australians fourth after serving a time penalty after a botched handover.
The win came despite Wilde squandering a lead at the start of the final leg after he went off course during the 300m swim.
But he recovered to split the front group of four with Benson over the 6.4km cycle before producing a faster 1.7km run split.
The race had started with USA’s Summer Rappaport, Britain’s Sophie Coldwell and Holland’s Maya Kingma breaking away on the first leg.
Rappaport’s superior running ability gave the USA a 7sec advantage for the changeover, but Coldwell handed over to Jonny Brownlee who produced the fastest split of the day to build a 14sec buffer for the 2016 European champion India Lee.
Unfortunately for the Brits, Lee was quickly reeled in by USA’s Taylor Knibb and New Zealand’s Nicole van Der Kaay, with Australia’s Ashleigh Gentle also pulling out a strong performance to thrust her nation back into contention.