The statement that best compares the work done by Leni Riefenstahl and Frank Capra to promote propaganda campaigns in their respective nations is:
Riefenstahl and Capra directed documentaries that supported the war effort in Germany and the U.S.
Both filmmakers are known for their influential works during World War II, with Riefenstahl creating films that glorified the Nazi regime and Capra producing films that rallied American support for the war effort.