The Olympic Sevens star scored a first half hat-trick as the Barbarians opened up a 29-12 interval lead at Glendale with Wales teammate Alisha Butchers and Ireland wing Ali Miller also touching down.
The USA powered back into the contest and captain Kate Zackary’s 78th minute converted try should have won the game.
But former Eagles lock Carmen Farmer won the ball back at the restart and the Barbarians midfield opened up the room for Joyce’s slashing run to the line.
The Barbarians brought together players from TEN different countries in the space of four days under head coach Anna Richards to take on a hungry and athletic Eagles outfit.
They had a wealth of experience, though, with captain Linda Itunu the major carrying threat and canny organisers in New Zealand veteran Emma Jensen and Wales’s adventurous Elinor Snowsill.
The Barbarians made a dream start from their first possession by moving the ball wide for Joyce to strike with just 40 seconds on the clock with Jensen converting and looking for more scores before an interception try from Amy Naber-Bonte and the first of two for Neariah Persinger edging the USA 12-7 in front.
That was the cue for a purple patch of attacking play from the Baa-baas with Joyce roaring over in the 28th and 30th minutes to complete her hat-trick with Jensen adding one conversion.
Miller got loose on the left to reach the line five minutes later and Butchers was involved twice in the final passage of play in the first half before scoring from close range.
Neither side could find an opening in the third quarter but the USA finally built up a head of steam with giant centre Eti Haungatau bulldozing her way over.
Suddenly the Baa-baas were in trouble as Persinger finished off an outstanding attack, then Zackary galloped over after Stacey Bridges’s great offload with three minutes to play.
But 697 caps is a huge amount of experience to put on the field and the unflustered response saw a hanging kick-off won in the air by Farmer.
Helen Nelson and Co in midfield had opened up space for their runners all night and Joyce surged through another hole to streak over for a dramatic final score with the final move.
That puts the women’s Barbarians record at played three, won three since making their debut against Munster 18 months ago. Now England await at Twickenham on June 2.
USA Women’s Eagles: Gabriella Cantorna, Jennine Duncan, Eti Haungatau, Amy Naber-Bonte, Neariah Persinger; Katana Howard, Carly Waters; Catherine Benson, Joanna Kitlinski, Nicole James, Stacey Bridges, Nicole Strasko, Katherine Zackary (Captain), Rachel Johnson, Nate Serevi.
Replacements: Katy Augustyn, Hope Rogers, Charli Jacoby, Alycia Washington, Joyce Taufa, Ashlee Byrge, Bui Baravilala, Bulou Mataitoga.
Barbarians: Jasmine Joyce (Worcester Valkyries & Wales); Tova Derk (Wasps), Amanda Thornborough (Westshore & Canada), Helen Nelson (Montpellier & Scotland, Vice-captain), Alison Miller (Old Belvedere & Ireland); Elinor Snowsill (Bristol Bears & Wales), Emma Jensen (Hastings & New Zealand); Rochelle Clark (Wasps & England), Fiao’o Fa’amausili (Auckland Marist & New Zealand), Steph Te Ohaere-Fox (Christchurch & New Zealand, Vice-captain), Carmen Farmer (Glendale & USA), Dalena Dennison (Warringah & Australia), Paula Fitzpatrick (St Mary’s & Ireland), Alisha Butchers (Worcester Valkyries & Wales), Linda Itunu (Ponsonby & New Zealand, Captain).
Replacements: Heather Kerr (Darlington MP & England), Samantha Martinez Gion (AAC Rugby Amsterdam & Netherlands), Gill Bourke (Stade Francais & Ireland), Julia Folk (Castaway Wdrs & Canada), Hannah Stolba (Glendale & USA), Andrea Burk (Capilanos & Canada), Katie Mason (Wasps & England).
Four-try Joyce clinches historic Barbarians win over USA – Barbarian FC