As to the Jewish question, the only serious contender that quickly comes to mind was Senator Joseph Liebermans' run for the Vice Presidency/Presidency a few years ago. I don't know why there haven't been more contenders through the years. I think this country would elect a Jewish President and I do not think most voters would automatically discount a Jewish contender just because of religion.
Of course John F. Kennedy was our first, and so far our only, Catholic President. His election proved that the American people would elect a Catholic President, and no doubt there will be others elected in the future. The biggest reason that no Catholic was elected President prior to JFK was the fear that a Catholic President might be controlled by the Vatican (Pope). The history of the Catholic Church tends to legitimize this fear to some extent.
The history of Europe in the last 1500 years is inextricably intertwined with the history of the Catholic Church. The Vatican held a virtual stranglehold over the European continent for many centuries and was the power behind the political institutions of the day. Much harm was done to many people for many many years in the name of religion. Of course religious conflict still exists all over the world.
Two of the founding principles of the United States were the freedom of religion and the separation of Church and State. These principles were the direct result of the lessons learned from the study of the history of Europe.
The Christian religion is divided into two basic camps, Catholic and Protestant. While the Protestant religion has fragmented into many sects (Lutheran, Methodist, Presbyterian, Baptist, etc.), the Catholic religion has remained centralized with power residing in the Pope and the Vatican. They still wield considerable power throughout the world and this power is still feared by many people.
As a group, Protestants outnumber Catholics by significant numbers in the United States. This voting block has kept the so called "Catholic menace" at bay for most of our history. Only JFK's skill as a politician enabled him to overcome the obstacles presented by his religion. I think he proved to most people that a President of the United States, who is of the Catholic faith, could lead this nation without being unduly influenced by the Pope or the political arm of the Vatican. I'm sure there will be others to come.
History is fascinating to me because I think to know where we are going, we first must know where we have been. I firmly believe in that the old saying, "Those who fail to learn from their mistakes are doomed to repeat them". The study of history is, in part, a study of those mistakes. Do you see a repetition of the past in the events taking place in the world today?
Interesting questions always make a person think. Thanks for your question.
Best wishes to you and yours.