The American topped the field of 15 on a hot and steamy Florida weekend; Canadians place 2nd and 3rd in the FEI Intermediate I CDI1*.
The American Olympic medalist emerged triumphant in her horse's first grand prix since suffering from a virus late last year.
Germany successfully defended their title, edging the US; Beatrice Boucher, Pia Fortmuller, Megan Lane and Evi Strasser rode for Canada.
This marks the second year in a row that Camille Carier Bergeron and Vanessa Creech-Terauds have partnered to win.
The Canadian Paralympian, who resides in England, won two Grade III classes with 'Wonky' in their first outing since the Tokyo Olympics.
Canadian squad is Beatrice Boucher/Summerwood’s Limei, Pia Fortmuller/Frieda, Megan Lane/Zodiac MW and Evi Strasser/Déjà vu Tyme.
Former Canadian Olympian Ashley Holzer, who took up American citizenship five years ago, tops the North American League with Havanna.
Aboard Lieutenant Lobin, Schloss attained some personal best scores, attributing them in part to a new saddle and recent vision therapy.
Dana Cooke placed third in the CCI3*-S riding Quatro; Holly Jacks-Smither and Candy King were 9th in the CCI4*-S division.
The pair took the sixth and last qualifier at ’s-Hertogenbosch in The Netherlands with a stunning Freestyle score of 90.555%.