Most of our forefathers who drafted the Constitution were secularists and Masons. Upon doing a little research, most websites, including www.midnightfreemasons.org say that he was not listed among the Freemasons, but “strong evidence exists that he was a member.” These people would not have wanted any religion established as an official religion of the United States, and that is why the First Amendment exists. Now to specifically answer my thoughts on your question: Jews were integrated into European society and culture dating way back (My great grandfather Kimmel’s Jewish roots have been traced back to 1392), but they don’t proselytize their religion. In fact they have a tendency to keep their religion and religious culture to themselves while integrating into the business community, especially banking and merchant trade. I think if our forefathers had any concerns about Jews, they would not have been religious in nature.
I don’t believe that Islam was a concern of James Madison et al because, although the Christians had fought a war against Muslims in an attempt to win back the Holy Land, no obvious threat existed at the time that the Islamic community would immigrate to the U.S.A.
I think at the time their concern was to keep the fanatical facets of Christianity from turning the new country into the same religious nightmare from which people risked life and limb to escape.