I think the Balfour Declaration would have amounted to something. It probably would have been a "swiss cheese" Israel, even more so than OTL, with Arab/Palestinian areas more clearly demarcated at the beginning. (I say at the beginning because that might have changed if the Arab states had wars with Israel as IOTL.) Although immigration could be limited when the area was a British protectorate, once it became an independent state, some version of aliyah would exist and immigration would be encouraged. I imagine many of the Polish and Russian Jews who died IOTL would have emigrated.
The butterflies that would necessarily arise from not having Nazis and WW2 could result in just about anything, though. Anything from a smaller Jewish homeland that's promptly overrun by the Arab states to a complete lack of Arab states capable of waging war on a much larger, more populous Israel.