The US did not support Israel past the original vote, rather it tried to push a series of measures that would have been detrimental to Israel. At the time Israel was far more reliant on the USSR.
Anyway, the US policy at the time was determined by the State Department which was very anti-Israel for various reasons. Truman overrode them for the US vote, but was too busy with other affairs to set policy afterwards.
Trump moved the US embassy to Jersusalem, and the US gives billions of aid to Israel. What is your criteria for "antisemitism"? If accepting the capital of Israel, giving money, military aid, is your definition of antisemetic it dimimishes Nazis activity if you group aid into "bullying" and "antisemitism".
I don't think that accurately describes US policy anymore, if it ever did. Modern day US administrations have withdrawn from the world, and that means their ME policies are not determined by reality, but by domestic ideologies and domestic political considerations.