No idea who you're referring to by "they", but the ones I mentioned are vehemently anti-Zionist. Many have left Israel. Those were just academics. May I remind you that there is a sizable population of Israeli Jews that are persecuted by the state for waving Palestinian flags, and Israeli Jews who actually call for the dissolution of Israel?
What are you disagreeing with?
But it wasn't American Jews who created Israel, rather it was a minority group among eastern European Jews. American Jews at the time, as with most global Jews, were anti-Zionist or neutral which is why Israel did not get much migrants from US or anywhere from the West. On the contrary, most European Jews preferred migrating to the US instead of Israel.
The vast majority of Israelis are from Soviet Union (Russia, Ukraine, Lithuania), Poland, and Hungary. Soviets played a major hand in exporting local Jews to Israel (which is why the most spoken language in Israel, after Hebrew, is Russian, not English).
American (Jewish and non-Jewish) endorsement of Israel is a later innovation, well after 1948. Even up until the Suez Crisis, Americans played no part, rather warning the belligerents (France, UK, Israel) not to attack Egypt, and then forcing a withdrawal via UN.
The fiercest anti-Zionist Jews are also American, the likes of Neturei Karta affiliates, Chomsky, Finkelstein, JVP, etc., while the biggest proponents of Herzl's Zionism today are American Christian Evangelicals, a sect that didn't have any major Zionist motives until after Israel's creation.