The swagger has arrived.

The United States began their Women's World Cup on Saturday in Auckland not just with a 3-0 win over Vietnam, but a Stars-and-Stripes statement off the field.

Eden Park's near-capacity 41,000 crowd was full of American patriots, with thousands clad in red white and blue facepaint, US kits and fan paraphernalia.

The squad, led by off-field icon Megan Rapinoe, sported custom fit suits made by Nike and London designer Martine Rose, paired with fluorescent space-age yellow shades as they travelled to Eden Park.

Rapinoe, who has swapped her 2019 World Cup-winning pink hair for a vibrant blue cut in New Zealand, described the fit in one word.

"Sensational," she said.

"Honestly, one of my best days as a US Soccer employee that I've ever had. And that's saying a lot."

With four triumphs in eight tournaments, the world No.1 Americans are the undisputed World Cup favourites, and looked the part off the pitch.

Whether they were as stylish on it is in dispute.

The best news for the US was Sophia Smith, who scored twice and assisted Lindsey Horan's third in a breakout performance.

Smith looms as a shooting star of the 2023 tournament, buzzing around striker Alex Morgan with intent, and bringing a sharpness other teammates lacked.

The final shot count, 28 to 1, hinted at what might have been possible if the Americans all brought their shooting boots.

"We're still finding it, a little bit," Rapinoe said.

"That always happens, you build into your best team and your best performances."

Kelley O'Hara was more succinct when asked to describe their performance.

"We got the W. That's the important part," she said, curtly.

Rapinoe, notched her 200th appearance for the national team, a welcome one for coach Vlatko Andonovski.

The superstar had been out for six weeks with a calf injury, but entered the pitch on the hour mark alongside Rose Lavelle, who hadn't played since April with a knee complaint.

"I've been feeling really good. I've been doing as much as I possibly can often feel to make sure that I ready for the team when, when I'm needed," Lavelle said.

"We would have liked to put a few more away but I think a win's a win."

A sterner test awaits the US next: a 2019 World Cup final rematch with the Netherlands on Thursday in Wellington.