I have read the novel "Ramona" a few times, and it seems something was lost when the book was translated into film. First of all, the story takes place in the Spanish colonial days of California, and this is why the Native Americans are speaking with Spanish accents. The "gringo" white people (Americans) are seen as the villains because they mostly are Protestant and are moving into a predominantly Catholic area and are claiming land that had been granted to Spanish settlers by the King of Spain. There was this same ill feeling about gringos or "white settlers" when Texas was in the process of separating from Mexico and becoming part of the United States.
As for Ramona's being a half-breed, the novel explains she is the child of the Spanish rancher and his Native American girl friend. The rancher brings her, as an infant, to the hacienda, and the rancher's wife agrees to bring up her husband's illegitimate daughter as if the child were her own or at least her social equal.
I am not sure of Loretta Young's heritage, but I believe she was a devout Catholic and perhaps was of Latin descent. It so happens her sister Georgiana was married to Ricardo Montalban, so Miss Young was associated with Latin Americans in her private life. Mr. Ameche was an Italian-American and no doubt Catholic, so he fit into this story of Spanish-colonial California very well.
I hope this explanation has helped some reviewers better understand the background of "Ramona." One of my favorite scenes is the priest coming to bless the flock of sheep and crops each spring. It is reminiscent of the same blessing in "The Thorn Birds" and the annual "Blessing of the Fleet" in the Gulf Coast area of the United States.