Already on April 13th 1933 Samuel Untermeyer said the following (very good article! "Hitler's Bitterst Foe"):

Our next act should be to see to it that nowhere in the world and under no circumstances should a Jew, from this day forth, buy or use merchandise manufactured in Germany or support Germany industry in any form. The action taken in that respect by the Jewish shopkeepers in London should be followed the world over. (8)In making this speech, Untermyer was aware that most of the leaders of the American Jewishcommunity, in particular the American Jewish Committee, opposed a trade boycott. The Jewish WarVeterans were the only mainstream Jewish organization that supported one. (9) It was also a difficultdecision for Untermyer as the son of German Jews. In a letter to his friend Colonel Edward M. House,President Woodrow Wilson's private adviser, the following year he explained that ...