I read the first three stories. The artwork was reasonably good. I liked the staging, especially that of the second and third stories. Yes, the authors seemed to know more about South America than the typical action-oriented story writers of US 1940s comic book stories. They knew something about the large German migrations to South America between 1880 and the 1930s, who would later be exploited by The Nazi leaders, as agents for them there. The writer of the third story even knew about Bernardo O'Higgins, having been the leader of Chile's revolution against Spanish rule, in the early 1800s, and based a rich land-holding loyalist friend of the unnamed South American country's president (who faced a coup and assassination attempt) character on the premise that that family still had ties to the ruling government, implying that the country in question is Chile. It is such kinds of details that help make the story seem a little more realistic to me, more than a plain story with a lack of connection to real history, or worse, a story with historical, geographical, or scientific errors that draw too much attention, taking the reader out of "living in the story", and thus, make the story unbelievable, and no fun to read.
The stories were reasonably believable, fast-moving, full of action, and had some nice suspense and story elements, like the attempted presidential assassination and coup, and the different pro and anti Nazi political factions.
I don't think that the coincidence that Senorita Rio looking much like the countess was so hard to swallow. I can believe that one of the main reasons she was chosen (accepted) to be a US agent in South America was the very fact that she bore a striking resemblance to her, and could be a valuable asset in dealing with Nazi agent activity in Brazil, needed at that moment. She wanted to avenge her lover's death. Maybe that was her only realistic ticket into that field, and she did so well on that assignment that she was kept on for other operations.
It's a comic book. It doesn't bother me that she always wears a red dress, which could be used by US enemies to keep track of her all the time. We can imagine that she often changes her makeup, hairstyle clothing type and colours. I'm used to seeing wall colours, sky colours, clothing colours change from panel to panel in the same scene. Think of 1962-1982 Gold Key comics. Their colourists were abysmal. When I had something crucial for understanding of action in my story dependent upon the colour of a certain object or area remaining the same, I made special notes for the colourist on a separate piece of paper, AND out in the margin of the original inked artwork. And yet, my request was NEVER heeded or fulfilled by the colourist. Carl Barks told me that that was his experience, as well. The colourisation of these stories was adequate (which I cannot always say about all 1940s action-based comics that I read).
All in all, it was a pleasurable experience to read those Senorita Rio stories. Some day, when I have some "dead time", I'll read some more of them.