This topic has probably been asked before, and perhaps answered using the same method. But since I don't know off the top of my head, I'll just present three brief but clear results from the General Social Survey.
People who are more intelligent and more politically liberal tend to be less religious. Jews (i.e. Ashkenazi Jews, if they're American) are both, so we'd expect them to be more atheistic. And everyone knows they are. But what about if we compare them to their white Gentile counterparts who are also smart and liberal?
The three graphs below show the responses of people who are white, identify as liberal in their political views (from "slightly" to "extremely" liberal), and score at least 120 on an IQ test (or, for the first graph where that didn't give a big sample size, an IQ of at least 114). That's what used to be called "college material" before everyone got into college. They are then split up by religious preference.
First, here's a graph showing how confident you are in the existence of god:
Christians are exactly the same, with just over 40% knowing god exists without a doubt, and less than 10% being atheists or agnostics. Remember that these Christians are white, college-material liberals. Not surprisingly the "no religion" group are much more doubtful of god's existence. Jews are in between, with just over 20% being sure and nearly 30% being atheists or agnostics. Even controlling for brains and liberalism, Jews are noticeably less religious than Christians.
The next graph shows attitudes about the Bible, not specified as the Old Testament or both it and the New Testament. Possible responses are, "1. The Bible is the actual word of God and is to be taken literally, word for word. 2. The Bible is the inspired word of God but not everything in it should be taken literally, word for word. 3. The Bible is an ancient book of fables, legends, history, and moral precepts recorded by men."
Again the Christian groups are identical, with about 25% saying it's legends, etc., not the inspired or actual word of god. No shock that the "no religion" folks hold that view overwhelmingly, about 85%. Again the Jews are in between, though closer to the "no religion" group, with a little over 60% holding the non-divine view.
Finally, there's how often people attend religious services (which type of services is left open and unspecified -- so, any services). The less frequent bars are lower down in each column:
Here we find a subtle but noticeable difference within Christians, reflecting the greater orientation among Catholics toward church ritual, compared to Protestants. The "no religion" people hardly go at all, those who do attend presumably not being "out" or accomodating the wishes of their religious friends and family. Jews once more are in between Christians and "no religion" people, closer to the latter. Those who attend services nearly every week, every week, or more than once a week make up about 30% of Protestants, 40% of Catholics, 2% of "no religion" people, and 7% of Jews.
Looking only at whites who are pretty smart and politically liberal, Jews still come out as far less religious regarding their beliefs about supernatural higher powers, their attitudes toward sacred texts, and their participation in ritual practices. If anything, they're more like those who profess no religion, making phrases like "Jewish atheism" somewhat redundant.
This uniquely Jewish tendency toward atheism must reflect some other difference between them and the goyim, not race, IQ, or liberalism. The ecology that the Ashkenazim are adapted to is white-collar financial work, often in the service of the state. So the religious lobe of their brain has evolved to take as its object of worship the technocracy and technology that can deliver him into paradise, not something superstitious like the grace of god, or something less supernatural but still transcendental like loving thy neighbor as thyself.
And of course there are differences in the religions that the Jew and the Christian are exposed to growing up. Both religions build on the Old Testament, but the New Testament has an exciting new cast of characters who illustrate moral points during dramatic narratives, whereas the Talmud can only come off to youngsters as pointless grown-up bickering about whether grandpa is allowed to clean out his earwax on the Sabbath or has to hire a shabbos goy to do it for him.
It cannot surprise us that what we call "Judaism" -- i.e., Rabbinic Judaism -- hasn't gone anywhere, while the world has been taken over by Christianity and Islam, the other successful Abrahamic religion that also stars a dramatic new figure not found in the Old Testament. What makes Judaism unappealing to would-be convert outsiders probably makes it unappealing to in-group members too. So, Jews' lack of enthusiasm for religion is understandable, apart from their low baseline as shaped by their managerial ecological niche.
All that really is left for them to get excited about is the stuff that would only appeal to insiders, and perhaps explicitly turn off the outsiders. But that shades so easily into ethnic, rather than religious, chauvinism that they'll just get excited about their ethnicity instead of their religion. And sure enough, "proud to be a Jew" refers to the accomplishments of those in their ethnic group, not the beliefs and practices of their religious group.
GSS variables used: race, polviews, wordsum, relig, god, bible, attend.