But I think it's important to remember that most American Jews are abandoning their Faith, intermarrying to non-Jews and not raising their children Jewish. Taking up liberal and communist ideology is the result of this.
Yes, from this Jewish perspective, I would agree that many if not most American Jews have been brainwashed (or have been victims of attempted brainwashings) with revisionist history lessons by their elders, especially with regard to the historical role of Franklin D. Roosevelt and the Democrats with respect to Jewish issues and the New Deal and the economy. Many are also ignorant of the antisemitism within the Soviet Union and Eastern Europe under communist regimes. Glad you point out that Marx himself was anti-Jewish, and not a Jew. (His German parents were Jews who converted to the Lutheran faith, in which Marx was raised.)
Taking up liberal and and communist ideology is the result of [American Jews abandoning their faith, intermarrying to non-Jews].
That's too broad of a generalization. Not all Jews who "abandon their faith" and/or intermarry are on the left, and some who are quite observant are on the left. Remember as well that a previous generation of American Jews, one which was in general more religiously observant than today's, voted for Franklin D. Roosevelt in even greater percentages than than today's Jews do for 'Rat presidential candidates.