Is there evidence to suggest that the internment of these groups of people created a tactical or military advantage for the USA? Was the internment necessary for the military victory of the USA?
Edit: I realize that "German American" is vague because a huge portion of people had German ancestry, and perhaps I should rephrase it and say "German immigrants"
Was there an advantage?
Nothing significant. It did give a convenience for the USA high command, but not in any of the ways you mentioned, military or tactical. The internment of the German-American's and Japanese-Americans allowed the United States high command to worry less about "spies" in the homeland and focus more on the overseas war.
Was It Necessary?
There can be dispute here and everyone can and will have their own opinion on the matter. Historians tend to think no and I would tend to agree with them. There weren't that many Japanese or German spies in the USA that would actually have effected the war.