For those of you not familiar with Australian history, Sir Isaac Isaacs was the first Australian-born person to be appointed as Governor-General, and the first viceroy in the British Empire of Jewish origin. In the 1940s, however, he courted controversy with the local Jewish community with his opposition to Zionism, considering it treason and disloyalty to the British Empire. WI, with some persistance, his views become mainstream and thus force the Jewish State in Palestine project to be abandoned? (One could make the POD earlier if s/he wanted to.)
There were plenty of influential British (and American) Jews with similar views.
But by the 1940s, the Zionist project is already in being. There are two reasons why "cancelling" the project becomes difficult:
1. The ~400,000 Jews already living in the Holy Land, speaking Hebrew, with significant pre-state institutions (the Yishuv) and even militias (the Haganah, Palmach, Etzel, and Lehi).
Can they be relocated or subordinated to a permanent international protectorate/Arab state/bin-national state? Maybe, though all of those have severe complications attached. But certainly something more than an intellectual solution is required.
2. The Jewish refugee population from Europe. I don't know when in the 40's your POD is, but post-conquest of Poland a LOT of Jews from at least Poland and Germany need somewhere to go that isn't Europe. And if any sort of Holocaust occurs - especially one as nasty as OTL's - that place will not be Europe. If it's significantly worse, then that population isn't a problem because few or none of them survive.
The abhorrence the vast majority of the survivors had for their home continent is attested by their preferring DP camps on Cyprus than returning home, and of course by the dramatic hunger strike on the Exodus. Do the US and Commonwealth throw open their doors to the emigration instead, and if so, why? OTL the bulk of the survivors flooded into Israel as soon as the British left, a tremendous material advantage to the young Jewish state.
Shortly after Israeli independence, the Jewish populations of the Islamic world departed virtually
en masse to Israel. From 1948 to 1958, the Jewish population of Israel rose from 800,000 to two million, mostly through immigration.
Having the Jewish populations of Central and Eastern Europe and the Islamic worlds "just stay home" is anything but an easy proposition. Possible, maybe, but you have to change their home conditions dramatically.
My point being simply that the '40s is too late simply to erase the Jewish settlement in Palestine by solely intellectual means. Turn Jewish opinion in the better off countries, like the US and UK, against it, sure - many were in OTL - but these populations never migrated to Israel in more than dribs and drabs in any case.
A much earlier POD (perhaps before or at the 1903 WZO Basel Conference) is possible. By WWI there was already an embryonic Yishuv, although its much smaller and its success was anything but guaranteed. You'd still need to figure out what happens to the Jewish populations in Eastern Europe and the Islamic World. "They just assimilate" doesn't really cut it; the economic and political conditions would have to be such that it was plausible.
Past WWII it gets much, much thornier, as I've hopefully demonstrated.