It would not be the first time that a well known city is divided and becomes symbolic home to a US President and pushed affairs to the potential brink of a world war,
Think of 1947 Berlin, the encirclement, the Airlift, the speech in which Kennedy declared himself to be a "Berliner", a citizen of that city.
Yes, if Trump declared himself to be the citizen of Jerusalem ( the Israeli sector I assume) that would give pause to the world. You do not attack The US president, or its rep with impunity ( US embassy in Tehran).