The European Allstars were just edged out by Team USA in a thrilling end to the Duel in the Pool event in Glasgow.
Boasting a 68-54 overnight lead in swimming's equivalent of golf's Ryder Cup, the Americans fought back to tie 131-131 after the scheduled 30 races.
But the United States, unbeaten in two previous meetings with Europe, took the mixed-relay tie-breaker to prevail.
The Americans needed a world record time of one minute and 37.17 seconds to beat the Europeans by just 0.2 seconds.
On the second day of competition, Britain's Fran Halsall (50m freestyle) and Sophie Allen (200m individual medley) both picked up individual wins for the Europeans while Spain's Mireia Belmonte added wins in the 800m freestyle and 200m butterfly to her two victories from the opening night.
But the Americans pulled themselves back into the contest with a sweep of the men's events, Conor Dwyer leading the way with a double over 200m freestyle and 200m individual medley.
Fran Halsall combined with Michelle Coleman, Jeanette Ottesen and Femke Heemskerk to take the last of the 30 events, the women's 4x100m freestyle.
She returned minutes later, anchoring the European quartet in the agonising tie-break decider.
"It's been a tough day," said Halsall. "We were ahead but we knew it was going to be touch and go as to who would win.
"It came down to the freestyle relays and the girls really got together as a unit and swam really well and broke the world record. That was fantastic to be a part of and I was really buzzing after that.
"I knew I'd have to calm back down and get ready for a swim-off and that was hard and emotional but so great to be a part of and I really enjoyed it.
"Standing up as a European team and being that close to the Americans with so many people behind you is something I will be proud of for a long time."
After a 200m breaststroke victory on the opening day, Olympic silver medallist Michael Jamieson broke the British record but narrowly missed out on points as he clocked 57.52 for fourth in the 100m breaststroke.
There were also British records for Sophie Allen in the 100m breaststroke (1:05.39) and 200m individual medley (2:05.90) while Jazz Carlin touched third with a Welsh record 8:12.01 in the 800m freestyle.
Jamieson said he could have no complaints with his form on his international homecoming.
"I'm really happy with my swim tonight," said the Scot. "That's 0.3 faster than my time at the Europeans last week, which is a new British record, so I'm delighted.
"I don't have the speed that those other guys have over 100m and can't match those tall guys over the front half.
"But the atmosphere was amazing again and it's so good to have so many people here and this kind of coverage."