This is an endless convo but i gotta say that i find Ralph Salerno's statement to be pretty realistic:

In November 1963, the national mafia commission and a number of major mob leaders were clearly threatened by dissension, enmity and treachery and the strongest effort as yet mounted against organized crime.

La Cosa Nostra had a strong motive for taking drastic action. Yet it is extremely unlikely that it would have considered such a major and dangerous act as assassinating the President, or, if it had, it would not have come to light. Thus there is a strange dichotomy. It also appears that most of the leaders were too preoccupied with personal problems to undertake such a venture on their own. Nor does the information developed by law enforcement agencies reveal any indication that any were planning or involved in such an endeavor.

An open question remains.

The question is still open, however, with respect to two individuals. Unfortunately, there is a substantial disparity in the quantity and quality of the FBI and other law enforcement intelligence efforts for Carlos Marcello of New Orleans and Santos Trafficante of Florida. Neither was subject to a direct electronic surveillance by the FBI in the time period of this study.

On February 15, 1963, the Director indicated disappointment memorandum which called for a "special effort" by the New Orleans office. In the latter part of 1963, Director Hoover ordered the compilation of reports on La Cosa Nostra from the major offices; these were to reach the Bureau and the New York City office (where the semiannual summary was prepared) by December 15, 1963. The memorandum reads in part:
Some cities have blind spots about La Cosa Nostra. It is well to note that we have experienced situations in which certain offices took the position that La Cosa Nostra did not exist in their respective territories, only to learn at a later date that this organization, with its typical family structure, is in fact in existence in the area and has been many years.

Dallas was another area in which the FBI was far less active against La Cosa Nostra. Although Joseph Francis Civello, a "counselor to the Italian community at large" according to the FBI, attended the Apalachin meeting in 1957, the Crime Condition Report filed by the Dallas field office for the period ending February 26, 1962, stated, "There is no evidence of illegal activity by Joseph Francis Civello." This same report concluded that "Texas is not a place where the Mafia has the kind of control it has elsewhere." Dallas also did not have in operation any electronic surveillance in 1963.

It is evident the Kennedy administration launched the strongest Federal effort ever against organized crime. Leaders and members of La Cosa Nostra were clearly concerned by it and blamed the President to some extent, but most definitely his brother, Atty. Gert. Robert F. Kennedy. It was also clear that organized crime would have benefitted from the assassination of John F. Kennedy and the changes it would bring in Government policy and officials. Nevertheless, it is extremely unlikely that the national commission of La Cosa Nostra was involved in any plan to kill the President. It was facing strong internal dissension and other problems and does not appear to have been in a position to undertake such a major act.

A review of the history of La Cosa Nostra in the United States reveals, moreover, no precedent for the assassination of a President. In fact, he is among several categories of people against whom organized crime traditionally has not committed acts of violence. Nor does the method of the assassination conform to the traditional pattern of organized crime murders-- it involved people who were not members of La Cosa Nostra, one of whom was unstable, it does not seem to have had any authorization from any leader, it was conducted without the usual precautions that protect the assassin from being apprehended, and the murder weapon was atypical. Nevertheless, there have been exceptions to the traditional pattern and the Kennedy assassination has parallels to these exceptions. Thus involvement by individual members of organized crime cannot be precluded.