Americans have a long tradition of divided loyalties going all the way back to the Colonial period, when many Colonists retained their loyalty to the Crown. In my grandfather's day many socialists who had come to America from Germany or Russia were deeply ambivalent about America's entry into the war. In the mid-twentieth century the most well known and widely discussed divided loyalty was of course the emotional and financial support given by Irish-Americans to the IRA at a time when the US government was labelling them a terrorist organization. One tends to forget that Joe McCarthy got his start representing a heavily German-American Congressional district and defending Germany against the condemnation of its WW II atrocities.
So the divided loyalty of American Jews with regard to Israel is not surprising. What I find disturbing is the unwillingness of many left-wing Jewish intellectuals to speak openly and honestly about their divided loyalty and either to defend Israel's apartheid policies and bellicose foreign policy or openly acknowledge their rejection of those policies. It is interesting that Israeli left intellectuals do not have that difficulty.