La Ross (Le Ross in the other broadsides) may not refer to an actual ship (or pirate), but "famed La Ross" implies that it probably does, as well as the way the name is dropped.

Furthermore, the mention of the French and Spanish being afflicted suggests that Barbary pirates are to blame, and Murad Rais's career was finally brought to an end when he was struck down by a cannonball, as in the song--1832. Just a coincidence?