HARRISON, N.J. -- Sunday had the air of an occasion. There was the pregame roar echoing out of stands full of the fans who gathered outside more than two hours before kickoff. There was a giant U.S. flag that swallowed the field as a World War II veteran played a hauntingly beautiful version of the national anthem on harmonica. There was even a rival against which to play.

But dressed up though it was, a 3-0 win against Mexico remained a dress rehearsal. It was a game that meant nothing to conclude a nearly three-year process that will determine everything.

The U.S. women want to play a certain way. They want to attack. They want to be on the front foot. They believe they have the talent and depth to pull it off for seven games in France that will grow more arduous by the game. For better or worse -- and there was a bit of both -- one more dry run was what Sunday was about.

"The principles are set, we know what we're doing," U.S. midfielder Julie Ertz said. "There's no changes there, which is great going into it because now we can really focus on finalizing those details and cleaning everything up."

-- U.S. women wrap up World Cup prep with easy win over Mexico

In a vacuum, the outcome of the send-off game is historically a poor predictor of World Cup fortunes. The United States and South Korea played to a uninspiring 0-0 draw four years ago at Red Bull Arena. The Americans made confetti angels and lifted the World Cup trophy barely a month later.

Even a 4-0 send-off win against Finland in 2007 offered few hints of what was to come a little more than a month later: a 4-0 loss to Brazil in the World Cup semifinals.

The margin of victory against Mexico, a team the U.S. women beat 6-0 at the start of a World Cup qualifying tournament in which Mexico stunningly failed to make the final round, doesn't much matter in the abstract. More telling is the fact that the United States created enough chances in the first half alone to lead by four or five goals.

Megan Rapinoe, Tobin Heath and Alex Morgan give the U.S. women a front line no team in the world can top. AP Photo/Julio Cortez

As has usually been the case in send-off games, including under coach Jill Ellis for both the 2015 World Cup and 2016 Olympics, the lineup against Mexico looked much like it can be expected to look for the opening game against Thailand on June 11. That begins, literally, with Tobin Heath, Alex Morgan and Megan Rapinoe applying pressure from a front line no team in the world can top.

No, Heath wasn't storming forward like a Jurgen Klopp acolyte when Mexico botched an attempt to play out of the back around the 11th minute. But she was close enough and alert enough to pounce on an errant pass from the goalkeeper, beat the lone defender and score low and hard back across the face of goal. Whether it's an all-out press to regain the ball or just lurking close enough to matter, the U.S. women want to force miscues and punish them.

Yet it's unavoidable that, with Sunday a microcosm, the United States has often been inefficient in finishing the chances it works to create. That should still be a net positive -- better to create chances you don't finish than to create few chances.

"I think we created a lot of chances," Ellis said. "I think the players would say as well, we can definitely be sharper in the final pass and inside the 18. ... This group creates a lot, and they're very potent. I think in time, we wear teams down."

But whether it was Heath putting a shot wide after a sensational setup from Rose Lavelle or Rapinoe overheating a shot amid the energy of the moment, the U.S. women left some goals on the board. All teams do. But at some point in the weeks ahead, they won't have that luxury.

"I think any time we have more opportunities, we want to put more of a percentage in the goal," Ertz said. "I think that's how we are. That's the standards we have. Of course we want to do better. But it's 90 minutes, and it's continuing to push and push and not get frustrated but continue to work as a team."

The game did little to resolve the most notable lingering lineup question for the Americans -- perhaps the only remaining question. Sam Mewis started again in midfield, ostensibly in place of Lindsey Horan. That is something of a theme this year. A U.S. Soccer official said the decision not to start Horan was due to "load management" rather than a specific new injury or tactical decision. She played the entire second half. But Mewis was again enough of a presence to make it a difficult choice for Ellis as to which two of Mewis, Horan and Lavelle to pair in front of Ertz.

Depth is a good problem to have. Even though the U.S. women won't have the luxury of six substitutions in France, as they were allowed against Mexico, Sunday showed again that they have it in abundance on the top two lines. Coming on as essentially a new line after halftime, Carli Lloyd, Christen Press and Mallory Pugh created both second-half goals, one from Pugh and one from Press, with Lloyd involved in both and narrowly missing out on one of her own.

"The subs that came in were huge game-changers for us," Ertz said. "They were ready and prepared, and it gave us a whole different dynamic up front. Yeah, definitely I think the first half was a little disappointing, not how well we wanted to play. But I did think we had good opportunities, and we had some good things happen. We take from that, and we learn."

Megan Rapinoe and the U.S. women head to France undefeated in their last nine games with four straight shutouts. Vincent Carchietta-USA TODAY Sports

Horan's second-half stint was a reminder that the best news that came out of Sunday's game was the lack of a significant injury report. Morgan drew out the trainers after getting her legs tangled with a defender on a near-goal in the first half but returned to the game immediately. Ertz collided with Kelley O'Hara on a header in the second half and stayed down briefly, but she returned after almost no time on the sideline. On a hot afternoon, goalkeeper Alyssa Naeher also received treatment for what appeared to be a leg cramp in the second half but remained in the game.

Injuries are just as possible in practice as in games, but the United States appears set to begin this World Cup with a relatively healthy roster, something rarely true over the past two years.

Perhaps the best perspective came from Abby Wambach, a newly named member of the National Soccer Hall of Fame. Speaking at halftime, Wambach noted how excited she is to see what is coming for a group whose journey is only just beginning.

"I just think that this team, we still haven't seen the potential that they could get to," Wambach said. "I think the coaching staff has probably been tinkering with this or that over the last 12 months, so right now it's fun to watch them get into their zone, everybody get into their roles. The team is set. So you see kind of that tension go away after this game."

The rehearsals are over. The U.S. women know their lines. Now the curtain goes up.