The contemporary connection drawn between the Jewish community and the Slave Trade comes primarily from work put forward by the Nation of Islam in the early 1990s titled The Secret Relationship. It is, unsurprisingly, hyperbolic bullshyt. Eli Faber released a comprehensive rebuttal later in the decade. Jews, Slaves, and the Slave Trade: Setting the Record Straight is (one of) the most meticulous accountings of Jewish involvement in the transatlantic slave trade. His findings are what you might expect, limited involvement and, where involvement is discernible, it almost involves Jewish merchants operating in an economic environment whose contours have been defined by non-Jewish merchants. They're (occasional) participants, not instigators. Faber identifies something like 100 slaves brought to Barbados in a ship with a Jewish owner or share-owner compared to over 45,000 from non-Jewish merchants. There is a litany of damning statistical evidence in his work.
Just as a side note, the Jewish community involved were Sephardic, Jews descended from those (mostly) expelled from the Iberian peninsula. Though rarely resident in the Iberian peninsula during the heyday of the Atlantic slave tiade, the Sephardic community had an onomastic tradition firmly grounded in a Hebrew-Andalusí Arabic-Spanish linguistic paradigm. Their names usually appear to modern readers as "Spanish", but most New World-resident Sephardic Jewish communities are associated with (and lived in) Dutch colonial enterprises (e.g. Recife, Curaçao). The American mainland Jewish communities likewise originated in immigrants to Dutch holdings (mostly New Amsterdam), but Newport, Rhode Island later attracts a significant community.
The link with the specifically American-flagged slave trade is almost certainly due to the involvement of Aaron Lopez - a Sephardic Jewish merchant from Rhode Island who was involved in the Slave Trade. Rhode Island briefly specializes in the Atlantic Slave Trade in the immediately pre- and post-Revolutionary period; the actors are overwhelmingly "American" (Yankee and French Huguenot mostly), but Lopez is certainly a prominent member of this clique. Old-line Yankees like the Brown's and established Huguenot-origin families like the D'Wolf's were much more active in this space than Lopez. The D'Wolf's, in particular, continue their slave trading activities post-1808 (when importation of slaves is banned) in Cuba for a few more decades. Still you could see how Newport's involvement in the Slave Trade and the size of its Jewish community (even those these two things don't really overlap chronologically) could lead people with an existing agenda to draw to a more explicit connection.