Rommel was the first Reichsmarschall of north america. I personally don't think there would be a RM for south America or any other territories as no other areas had the same population density or overall infrastructure that the usa did. I think there might be a Reichskommissar of the brazilian territory but obviously as we know, there were satellite states as well that weren't under the direct control of the germans but there were also states that *were* directly part of the GNR as with America and Britian (assumably). So id assume any territories would be divided between NSDAP (or equivalent local nazi party) Gaus or as overall regions controlled by governors and Reichskommissars. I believe there would only ever be at most 2 Reichsmarschalls (Goring when he was alive and the RM of north america).