I'm going to go out on a limb here, and suggest it may possibly be due to the powerful influence exerted by the Jewish lobbies in the Senate and House of Congress, and the fact that it's good business which keeps folk in the munitions and armaments industries in jobs, but I'm sure that's just my cynical view, and they are really acting out of altruism and concern for their fellow human beings after all, because if there's one thing the US cares about it's upholding freedom, morality and justice for all.