Tyla Nathan-Wong doubled the lead right on halftime, crossing between the posts to give the Black Ferns a 14-0 lead at the break.
New Zealand are on the same side of the draw as Ireland and the United States, avoiding hard fixtures against Australia and the unbeaten Canada.
Ghislaine Landry's Canada were particularly dominant, beating Russian Federation 34-7, Argentina 38-7 and France 21-7, backing up their victorious performance in Sydney and laying down a marker for their rivals in knock-out play on Saturday.
Their biggest test will come when they meet their 2016 Rio Olympic final conquerors Australia early on Saturday afternoon (NZ time) in Pool C.
"But we are delighted with this win, we're going to enjoy it and then look ahead to the next tournament and see how we go from there". There they'll be joined by Argentina, Brazil and Spain.
The hosts remain in contention for their first-ever World Rugby Sevens Series title on home soil and will go up against current overall leaders South Africa, who beat Australia 17-14 in their quarter-final, in the last four.
"We continued to work for each other and fight for each other", U.S. captain Madison Hughes said.
Australia will play New Zealand in the final of the Las Vegas women's rugby sevens tournament after New Zealand accounted for the United States 12-7 in a tight semi-final on Sunday (AEDT).