Michaela Blyde cracked the staunch American defence early on to put the Black Ferns Sevens ahead, but then after conceding a couple of penalties, the host nation pounced on this and shot through with two tries of their own to take the lead at the break.
New Zealand's patient determination showed, and after a halftime team talk the tournament favourites prevailed with tries to Gayle Broughton and Portia Woodman sealing the tight win.
Teammate Tyla Nathan-Wong says the message at halftime was simply keeping cool heads.
"In sevens, 14 minutes may not seem long, but really those minutes tick away really slowly.
"We just looked at each other, composed ourselves, and really brought it to them".
The Black Ferns' final hurdle to a first ever successful Sevens World Cup title defence is every Kiwi rugby fan's worst nightmare - France in the grand final.
The French women have done exactly what their male counterparts did yesterday – eliminate Australia from the competition.
France are the tournament's sixth seeds but they did finish third on the Sevens Series standings including a second placing at the Japan Sevens where they were defeated by New Zealand in the final.
Nathan-Wong says they'll spend the coming hours analysing France by video.
"Big ups to France, they've been improving throughout the series and made their first ever world series final against us in Japan, so we know it'll be a tough 14 minutes against them."
"We'll go back, rest and recover, do some video analysis and be ready to fire".
The final will be played at 2:47pm [NZT], while the All Blacks Sevens also meet France to continue their title defence, with that quarterfinal match-up set for 11:16am NZT.