And they made it three five-pointers out of three after a cracking contest.
USA, ranked seventh in the world, finished third in the pool and also go through to the last eight and will have taken heart from part of their performance too.
Canada got off to a flying start and they took the lead thanks to a try from an attacking lineout.
Hooker Emily Tuttosi was the scorer, her sixth of an amazing tournament so far, and although captain Sophie De Goede missed the conversion they were 5-0 up after six minutes.
Things got even better for them 10 minutes later when fly-half Alex Tessier went over for try number two and this time De Goede did add the extras and they were in the driving seat at 12-0 to the good.
USA are made of stern stuff, though, and their centre Alev Kelter is certainly a tough cookie.
In the 21st minute she injected some momentum into her side's performance by scoring a try and converting it.
Three minutes before half-time Canada scored an important third try. It came through winger Paige Farries and, with De Goede converting, it was 19-7 to them with 40 minutes remaining.
USA knew that they needed to score first in the second half, and they so nearly did just that.
In fact, they thought they had scored in the 54th minute, but, after checking with her TMO, referee Aimee Barrett-Theron disallowed the try following an obstruction by second-row Evi Ashenbrucker in the build-up.
Canada managed to ride out that period of pressure and get back down the other end of the pitch to bag their bonus-point fourth try on the hour mark.
It came after a good break, kick and chase from centre Alysha Corrigan.
The chase by Corrigan won a penalty and, from the resultant lineout, replacement front-row Olivia DeMerchant went over. De Goede’s conversion attempt hit the bar, but her side were 24-7 up.
A try by USA’s impressive captain Kate Zackary in the 71st minute – converted by Kelter – brought them back within 10 points.
However, with a minute remaining number eight Zackary was yellow-carded and Canada took advantage to put the cherry on top of their cake with try number five.
The try came from replacement front-row Mikiela Nelson and, after the match, De Goede said: “We are pleased with the performance, and we want to take momentum into the knockout stages now.”