Wolfgang, wouldn't a citizen of Hamburg say "Ich bin Hamburger" rather than "Ich bin ein Hamburger"?   And likewise, "Ich bin Wiener", and so forth? What you say refers to something like JFK's goof, that "I am a jelly doughnut" rather than "I am a Berlin resident", I thought.

Admittedly, my command of German is pretty sketchy, so correct me if I'm wrong.

Dave Oesterreich