The Guardian imagines a 'powerful American Jewish lobby'…in the 1940s!

A Jan. 26th article in the Guardian written by Michael White (What would Winston Churchill have made of King Abdullah’s death?) included the following passages:

…Churchill had supported the 1916 Balfour Declaration in favour of a Jewish national homeland, issued for a mixed bag of motives, including wanting Zionist support against the Kaiser but also fashionable self-determination.
Right from the start Palestine’s Arabs got overlooked, but when Britain got a League of Nations mandate there they promptly made their presence loudly felt.
What an imperial burden that proved to be for the fading British imperialists, though Churchill resisted further decolonisation when he returned to power (1951-55). By this time Israel had fought and won its 1948 war of independence against its Arab neighbours and the grim cycle we live with today had begun.
Even in the war Churchill experienced a sharp bit of that. Angry that London appeared to be tilting towards the Arabs – banning local land sales to Jewish immigrants for example – and fearful that [Lord] Balfour’s pledge would be lost, militant Zionists – with the support of the increasingly powerful Jewish lobby in the US – staged attacks on the British regime, culminating in the 1944 murder in Cairo of Lord Moyne, British regional supremo, a friend and cabinet colleague of Churchill’s.

First, the suggestion that the “Jewish lobby” was powerful during WWII is absurd. The American Jewish community during the 30s and 40s was largely weak and divided, lacking the confidence and relative unity that later generations of Jewish leaders would take for granted.
In fact, “mainstream Jewish organizations held a relatively low profile” during the Holocaust, and were hesitant to even lobby the Roosevelt and Truman Administrations to save Jews facing annihilation in Europe.

As historian Peter Egill Brownfeld, in an article for The American Council for Judaism, noted:

[Jews] wanted to avoid the appearance of controlling a Jewish lobby, separated from other American interests. In a climate of worldwide anti-Semitism – something that had also grown in America in the 1930s – they feared the impact of any actions other than patriotically concentrating on victory.
…
In 1943, the first verified information about the holocaust emerged from Europe. The news garnered little press attention and was buried in all of the major newspapers. It appeared in the New York Times in a seven and a half-inch report on page ten. The Washington Post gave it just three inches on page six.
 
[Peter S Bergson] and his colleagues – young Jewish activists, many of whom were from Palestine – changed their focus when this news came out. Bergson’s group began to concentrate on publicizing the German efforts to annihilate the Jews. They formed a new organization to take the place of CJA – the Emergency Committee to Save the Jewish People of Europe.
Bergson recalled that after his group learned about what was happening in Europe, its first inclination was to work with the mainstream Jewish organizations. “After the story in the Washington Post, the first thing we did was try to go to them and were flabbergasted when we couldn’t move them,” Bergson recalled. “We said, `look, something has to be done – there’s a fire. Something has to be done about saving the Jews.’” But Bergson found their passivity impossible to work with. When he asked for help from the leading Jewish organizations, he found no interest for the kind of radical push for rescue in which he was interested.  

Further, contrary to the Guardian’s suggestion to the contrary, the American “Jewish lobby” – and mainstream Zionist groups in Palestine and the US more broadly – almost universally strongly opposed attacks on British targets by ‘militant Zionists’. 
As Robert Rosen wrote in his book Saving the Jews: Franklin D. Roosevelt and the Holocaust, support for attacks by Zionist groups (such as the Irgun) in Palestine only existed on the fringes of the American Zionist community. Most mainstream Jewish groups strongly opposed their tactics. 
Here’s an excerpt from his book (via Google Books):
It’s bad enough that the hard left in the UK continues to warn of the undue influence of tiny Jewish communities in the US and Europe. But, to impute such power to Jews prior to and during the Holocaust is grossly ahistorical, and evokes the unhinged Judeophobic hyperbole advanced throughout that era by decidedly reactionary political figures.