Australian Hugo Weaving, American Stanley Tucci, and Englishmen Toby Jones and Richard Armitage play Germans.
Englishman Dominic Cooper as Howard Stark, American playboy and captain of industry.
Englishman David Bradley as the Norwegian keeper of the Cosmic Cube.
Romanian-born Sebastian Stan as American Bucky Barnes.
Was actually deliberately averted in the case of Captain America himself. The crew felt that it was necessary for the Cap to be played by a genuine American.
Thoroughly averted in the case of Neal McDonough as Dum-Dum Dugan, who shares the same nationality and home city of Boston, Mass, as well as Irish lineage, as well as Bruno Ricci (who is actually French) as Jacques Dernier.
English Natalie Dormer as the American soldier who kisses the Captain.
Up until a very late stage in pre-production, Hydra would have been a blatantly Nazi paramilitary organization, with Swastikas on their uniform. The implication is still present in the final version, however.
In addition, deleted scenes also had HYDRA explicitly attacking Nazis in addition to Allied powers.