Oh no, not that stupid “I am a jelly donut” urban legend again.
Before John F. Kennedy delivered his speech, the final draft was read by Willy Brandt, mayor of West Berlin and future chancellor of West Germany. Brandt was as fluent in English as he was in German, and Kennedy was his guest and leader of West Germany’s most powerful NATO ally. There was no way he would have allowed Kennedy to embarrass himself by using the wrong metaphor in a speech.
The Berlin Wall had been erected shortly before Kennedy visited West Berlin, an island of democracy inside East Germany, which is why Stalin tried to force the United States, France and Britain to move out and leave Berlin entirely Soviet-controlled. (Denied use of railroads and the Autobahn, the United States retaliated with the Berlin Airlift, which continued for more than a year before Stalin finally gave up.)
The Wall made West Berliners feel even more threatened and isolated than they had been since the Airlift years. From the context of Kennedy’s speech, it was perfectly clear to the West Berliners that when he said “Ich bin ein Berliner,” he was saying that all free people of the world identified with them.