Trump intended the song as a moral lesson against indiscriminate admission of immigrants, meaning especially admission of Muslims, but there is no reason whatsoever why it could not also be a warning against Jews.
In fact it is much more aptly applied to the Jews, given the way Jews have taken over and have been wrecking the United States over the past century, a story that has been repeated over and over throughout the history of the Jews. In fact Jews are the fundamental creators of whatever Muslim problem exists in the United States today, through their influence on immigration-policy and incitement of foreign wars that have destabilized the Muslim world. The notion that there is some obligation to take refugees is certainly perpetuated by Jews.
Jews catch that kind of implication even when the general public does not -- even when it wasn't intended that way. You cannot try to save your country without running afoul of Jews.
Rush Limbaugh and others are attributing the song to Negro soul-singer Al Wilson, but Wilson was only one singer who recorded the song. (Johnny Rivers was another.) The song was written by Oscar Brown, Jr. (a mulatto) based on an ancient Greek tale attributed to Aesop, The Farmer and the Snake.
Here is the Aesop's fable:
ONE WINTER a Farmer found a Snake stiff and frozen with cold. He had compassion on it, and taking it up, placed it in his bosom. The Snake was quickly revived by the warmth, and resuming its natural instincts, bit its benefactor, inflicting on him a mortal wound. “Oh,” cried the Farmer with his last breath, “I am rightly served for pitying a scoundrel.”
The greatest kindness will not win the loyalty of ingrates.