i don't know if you have found the information elsewhere but the 1964/65 was never an official BIE World's Fair.
The official one were 1962 Seattle and 1967 Montreal but Robert Moses ignored the BIE.
The insults were probably the straw that broke the BIE back, but the fact that in 1967 Montreal was hosting the official fair and Montreal is only a few hours away from New York, the BIE did not want one so close both time wise and geographically close to Montreal. If it had been in Atlanta, they might have given permission.
This website explains what happened.
In order to accomplish his goals Moses had determined that the Fair must operate for two seasons. Additionally he would charge exhibitors rental fees for the site they would occupy at the Fair. These plans were a direct violation of B.I.E. rules. That and the fact that a Universal Exposition was already sanctioned within the ten-year-span limit put the B.I.E. and the New York World's Fair Corporation, in the formidable form of Robert Moses, in direct conflict.
Perhaps the B.I.E. would have been able to come to a compromise with New York had not Mr. Moses decided to make an issue of their differences. His insulting comments to the press regarding the B.I.E. and their rules so angered B.I.E. officials that they not only took the action of denying New York official permission to host the Fair in 1964; they specifically requested their member nations not to participate in the New York World's Fair!
This created a rather awkward situation back in New York. How can it be a World'sFair if the world can't come? As a result of the B.I.E. decision the list of International participants contains some noticeable absences with Canada, Great Britain, Italy, Germany and Australia among those choosing not to exhibit. To be sure, in the end, there were many International participants. However most were hosted by industrial or tourist interests in lieu of official government sponsorship.