User blog comment:KennyChief/S.H.I.E.L.D. is a UNITED STATES GOVERNMENT organization, not International./@comment-6127681-20151013043349/@comment-996391-20151015164648

I'd say the Reichsadler was used only because between 1934 and 1945 HYDRA was an exclusively German organization (you can even see  Großdeutsches Reich - Hydra Abteilung written on some documents), but after 1945 it became international.