For those not in the know, JFK immortalized the pastry from Berlin in his famous "Ich bin ein Berliner" speech.
"Ich bin Berliner" -> I'm a citizen of Berlin
"Ich bin ein Berliner" -> I'm a jelly donut.
Also, as a native German speaker, saying "Ich bin ein Berliner" is not unusual if you are talking about being a citizen of Berlin.
I don't think that was a common association at the time as well. Especially since (pastry) "Berliners" are not called "Berliners" in Berlin but "Pfannkuchen" instead.
Speaking of which, good thing Kennedy never visited Hamburg.
Compare "Danish" as an American term for a Viennese pastry, "he's Danish" doesn't sound odd.
We don't generally abbreviate foods named after places, but:
"Cheddar is 200 miles from both Sandwich and Stilton."
These are all places in England.
I'm not German nor a linguist, YMMV.
I agree that no native speaker would think of the pastry when hearing "Ich bin ein Berliner." Just like I wouldn't think of a sausage if someone were to say "Ich bin ein Frankfurter."
Sometimes they're even sold as "Donut".
[0] https://en.wikipedia.org/wiki/Ich_bin_ein_Berliner#%22I_am_a...
[1] https://language.mki.wisc.edu/essays/ich-bin-ein-berliner/
Of course you can say "Ich bin Clown" just as you can say "Ich bin Kaminfeger" or "Ich bin Physiotherapeut"
Edit: what chiki said
FWIW, I'm not a native speaker but I did study German in high school and college, and used my moderate proficiency extensively while traveling in Germany (including Berlin in 1990), and Austria, and living in Prague. I've laughed with native Germans about the JFK speech (which story was first related to me by my hs German teacher), and regardless of its provenance / veracity, it makes for an interesting discussion. :)
There's also a European liquor, bright blue in color, aptly named "Blau" (which word, "blau", is slang for drunk or intoxicated).
As for varieties of sausage, "wieners" (Wien/Vienna), and Frankfurters (Frankfurt) were referred to as "hot dogs" by Parisian college students jokingly(?) describing their mysterious ingredients... (citation needed, but I did read that in a seemingly-reputable magazine.)