Team USA bested New Zealand in dramatic fashion by 8 seconds after dropping Sunday's first race to go down 0-3 against Emirates Team New Zealand.
The clutch victory gave the Americans hope they could retain the trophy in the best-of-17 regatta.
Team USA had a 6-second lead at the first mark of Race 4 and a 16-second advantage at third mark, but New Zealand narrowed the gap to 5 seconds by the fourth, the San Jose Mercury News reported.
But the Americans lengthened their lead down the stretch.
The official score remained 3-0 for New Zealand because the Americans were penalized two races over cheating allegations at last year's America's Cup World Series.