The US boys had less success with only four of the eight in action on Sunday advancing to the second round.
Martin Redlicki and Dan Kerznerman had impressive wins, with Redlicki defeating Matej Maruscak of Slovakia 6-3, 6-4 and Kerznerman, a New Yorker with plenty of support on Court 8, downing Harry Bourchier of Australia 6-1 6-3.
The only seeded US boy, No. 5 Stefan Kozlov, showed little energy in his puzzlingly routine 6-1, 6-2 loss to Lucas Miedler of Austria, and wild cards Tommy Paul and JC Aragone went out quickly to seeded players, but two other wild cards, Kalamazoo champion Collin Altamirano and Mackenzie McDonald posted victories in late afternoon matches.
Altamirano suffered something of a letdown midway through the first set of his match with Korean Duck Hee Lee, but rededicated himself in the second set to post a 7-6(4), 6-1 victory.
"I got too comfortable in the match," said the 17-year-old from Yuba City, Calif. "I felt I could serve my way through the first set and not have to work as hard, and it was just sloppy. He just kind of stuck around, and I was playing sloppy points and sloppy games, but credit to him, he played good points. I got the tiebreaker and then got my head straight. I played a good couple of games in the second, and he was done."
Altamirano had 10 aces in the match, and even well into the second set, Lee, 15, couldn't read it.
"He had a really tough time with my serve," said Altamirano, who didn't know that Lee is deaf. "I don't know exactly what it was, but it was like he couldn't see it. I got him so many times when he didn't move, and it made me feel kind of good about myself, but yeah, he had a real tough time picking up my serve."
McDonald was facing his doubles partner and No. 7 seed Guillermo Nunez of Chile in his first round match, but the confidence he has gained this summer, particularly in qualifying for the ATP Masters in Cincinnati last month, led him to a come-from-behind 3-6, 7-6(5), 6-3 win.
"It's just all mental, I feel," said the 18-year-old from Piedmont, Calif. "I'm just happy I was able to stay focused and pull it out."
McDonald also appreciated the support he received during the match from USTA head of men's tennis Jay Berger and head of coaching Jose Higueras.
"I stepped it up in the tiebreaker," said McDonald. "I got pumped up, and I knew I had to. I think the crowd helped me a little bit in the tiebreaker. I saw Jay over there, and Jose, and that kind of bumped me up. Jay was very supportive, saying let's go Mackie, and Jose, and that actually did help me in the tiebreaker for sure."
The last game was a struggle for McDonald, who saved multiple break points before finally converting, with McDonald again giving credit to his mental approach.
"I felt I'm playing good tennis and as long as I can keep focus and keep playing good points and construct them and put them back-to-back together, I think I'll be fine. On the ad-out point, all I had to do is relax and I told myself that, and I won the next one, two, three points."
Sixteen more Americans, including all seven qualifiers, are scheduled to play on Monday, and the top seeds--Switzerland's Belinda Bencic and Germany Alexander Zverev--also take the courts for their first round matches.
The doubles draws were also released today, with a few first round doubles matches on the schedule for Monday.
See usopen.org for the draws.