Cinderella (GB), by Blue Ruin or Tomahawk x Manna, by Brown Bread, who was imported to the USA as a yearling. She was the dam of Hastings and Plaudit, whose sire lines carry on today through horses such as Relaunch, In Reality, and Holy Bull. She was also the granddam of Preakness winner Buskin, and her female line carries on through Opening Verse, Patchen Beauty, etc.
Scapa Flow meets the criteria in every respect, except she was British. Her sons were Fairway and Pharos. Her daughter Fair Isle won the One Thousand Guineas and went on to found a highly successful family. In particular her great-great-great grand daughter was broodmare of the year Reprocolor, dam of Colorspin, winner of the Irish Oaks. Colorspin is the dam of multiple stakes winner Kayf Tara.
I'm Avalyn Hunter, an author, pedigree researcher and longtime racing fan.