In today's second race, Oracle skipper JImmy Spithill was quicker off the start-line and powered into the first mark three seconds ahead.
Significantly, it was the first time Emirates Team NZ had trailed at the end of the first leg.
After lagging 12 seconds behind at the third mark, the Kiwis did actually edge ahead over the fourth downwind leg, turning six seconds up at the next gate.
But they seemed to miscalculate the fifth mark, had to tack behind Oracle and lost their lead. They could not make up the lost ground over the remaining distance.
"That was exactly what the boys needed," said Spithill. "We fought hard and it was good to see the boys keep their composure too - we lost that lead, but we were able to get that pass back at the top.
"I think there was a good improvement on boat speed today and I think another step tomorrow will be great.
"We worked very very hard those five days, we sailed probably five times as much as those other guys, a lot of work on the shore and it was great to see the boat going quicker.
"A little bit more tonight, a little improvement in sailing technique as well and we'll have a good shot tomorrow to take a couple more wins."
Burling seemed unfazed by the setback.
"It was great to see those boys sailing a little bit better," he offered. "We were really pleased with the way the boys fought back in that second race.
"We always knew it would be hard if these guys sail well and we're excited about the battle ahead.
"We're set up for a battle, we've worked hard over the past week as well and it's good to see them giving us one."
Earlier, Team New Zealand moved one step closer to America's Cup glory and within just three wins away from lifting the Auld Mug.
Spithill made a big tactical mistake at the start, gaining the best position on the line, but encroaching early for a two-boat length penalty.
Team NZ led by a few seconds around the first two marks, but helmsman Peter Burling had to withstand Spithill's aggression and a faster Oracle ACC boat upwind in 11-knot breezes.
The American team actually took the lead briefly up the third beat, but copped another two-length penalty for crossing too close to the NZ boat. That proved the decisive moment of the race and soon afterwards, Oracle fell off their foils in a gybe, to concede several hundred metres.
"We just approached this like any other race," said Burling afterwards. "It was nice to have five days off, and give the shore crew a good opportunity to work on the boat and make this great boat we've got a little bit quicker.
"We also managed to get out for three training sessions as well, to sharpen up all those little things, those little scenarios. That really showed today in the pre-start - we probably didn't milk that penalty as much as we should have.
"But to have full confidence in our strategy and our plan up that second beat, and force the issue, force the penalty and win the race was really pleasing for us.
"We've been excpecting these races to be a bit tighter like that, but we feel we've got really good boat-opn-boat stuff now to be able to deal with it."
The Americans' win now means their defence could extend at least into Tuesday (NZ time), and it gives them a little momentum that will have the Kiwis looked over their shoulders and thinking of San Francisco four years ago.
35th America's Cup match
Oracle Team USA v Emirates Team New Zealand
Race 5: Emirates Team NZ beat Oracle Team USA by two minutes 4 secs (NZ 4-0)
Race 6: Oracle Team USA beat Emirates Team New Zealand by11 secs (NZ 4-1)
