We've discussed it before. It was the IfNotNow of the 1940s and 1950s, holding an anti-Zionist position that it pretended was Jewish. The ACJ pretended to be loyal to "classical Reform Judaism," and insisted that Jews were a religion but not a people and that to be Zionist was to be anti-American. In 1957 the Union for Reform Judaism emphatically rejected the ACJ as having nothing to do with the Reform stance towards Zionism.
Because it had the name "Judaism" in its name, the media loved to quote it even though it represented only a fringe of a fringe of American Jewry. Just like "Jewish Voice for Peace" today, the early head of ACJ - Elmer Berger - managed to grab headlines and make it appear that ACJ was a major player in American Judaism.
So whatever happened to the ACJ?
It is still around, and even more irrelevant.
It has a website, and apparently it still has some assets, but not much income.
The website shows that there is a quarterly journal, "Issues of the American Council of Judaism." Nearly every article for the past twelve years is written by the same person, Allan C. Brownfeld.
Brownfeld, in a good As-A-Jew tradition, also writes for anti-Israel outlets like Mondoweiss and the Washington Report for Middle East Affairs.
If you want to know what JVP and IfNotNow will look like in ten years, look at the American Council of Judaism.