Hmm... well, one thing Perez did was have Amazons imprint themselves upon little girls who were rescued from shipwrecks or boating accidents. Spiritually speaking, those girls and their descendents (regardless of gender) were at least partially Amazon because of it. Julia Kapatelis is one such example, which is one reason why Diana and the Kapatelis family clicked as beautifully as they did. Who's to say that Betsy Ross isn't another such girl, or a descendent thereof? If so, then having the Amazons "inspire" the American flag, and having that flag later be taken as an important symbol by the Amazons helps to bring it full circle.
Diana Rockwell Trevor may or may not have an "Amazon spirit." The power of the story comes from Diana Rockwell being an outsider, and her having the spirit would be very elegant but it could also rob the story of some of its power. I have not yet chosen a stance in that regard.