Churchill was intent in bringing the United States into the European war, and it is conceivable that he would have succeeded if Pearl Harbor had not done the job.
Roosevelt was in an incremental process toward war, not all that different from Wilson's road to participating in World War I.
Moreover, the US was as deeply divided as it is on Obama's proposal to confirm his agreement with Iran. Roosevelt won a vote by a margin of one in the House of Representatives about the draft, against isolationists who wanted no part in Europe's war.
A worrying difference between Franklin and Barack is that Franklin wanted to act against the evil of the Nazis, while Barack is going along with the evil associated with one variety of Islamic extremism. And while Franklin was explicit in recognizing the evil of the Nazis, Barack occasionally sounds like a wannabee who can't see evil in anything Islamic.
In both cases the interests of Jews were both prominent and problematic.
There is a similarity between the nuttiness that asserts Barack Obama was not born in the US and/or is a Muslim, and the assertion that Franklin Roosevelt was anti-Semitic. One can find some of the same people asserting both varieties of the absurd.
Neither charge stands up to serious analysis, yet for both Roosevelt and Obama Jews were a significant problem. And for Jews, both Roosevelt and Obama provoked concerns.
Between the two Presidents, the status of Jews has changed dramatically. In Roosevelt's time, European Jews within the Nazi orbit were a helpless multitude, and Jews in the United States were a poor, marginally integrated group of mostly recent immigrants, with severely limited political status and less weight in national politics than anti-Semites. While some ranking officials in his administration did all they could to facilitate the entry of Jewish refugees to the United States, others did all they could to oppose the granting of visas to Jews.
Involved in Roosevelt's efforts to help Britain in its war, to get ready for extensive American participation, and then to engage full scale after Pearl Harbor, was his concern not to make the war appear to be something for the sake of Jews. Some were both anti-Semites and isolationists; a distaste for Jews, and a reluctance to shed blood and treasure for the sake of Jews went hand in hand.
American Jews themselves were ambivalent with respect to pressuring the White House for the sake of European Jews. While many raised money and demonstrated for the sake of European Jews, others accepted their fate and showed greater concern for their own marginal status as Americans. The New York Times--owned and staffed by Jews--tended to bury in inner pages, if it published at all, news about the slaughter of Jews at the hands of the Nazis.
Now American Jews, using all the status, position, and resources achieved, are lining up on both sides of the agreement with Iran and either condemning, praising, or accepting Netanyahu's campaign against it.
Obama's singling out Israel as his principal opponent is more public and prominent than Roosevelt's comments that he could not make America's war something for the sake of Jews.
It's no surprise that Jews, despite their achievements, and no matter what their attitudes about Iran, are uncomfortable with the Israel-centered politics. They are not all that far from concerns about dual loyalties and other nastiness. Anti-Semitism has retreated, but has by no means disappeared, and may be resurgent. And with it are Jews who join with Gentiles for asserting their opposition to what other Jews claim is essential.
Israel's status and capacity is nothing like what was available to European Jews in the 1940s.
Its capacities range from what is recognized as the region's most powerful military, with a theoretical ability to bring down Iran's nuclear facilities in apocalyptic fashion, or--more likely--to get along with a nuclear Iran in a framework of MAD (mutually assured destruction) of the kind that worked in the Cold War between the Soviet Union, China, the US, Britain, and France, and has lasted through several crises between India and Pakistan.
Due to its political standing, economic resources, and military options, Israel also has a capacity to force itself into the awareness of American, European, Iranian, and other governments, and achieve reasonable ways of getting along, despite BDS and other animosity fanned by Palestinians, some Jews, and others, some of whom are marginal or overt anti-Semites.
If Israel has legitimate reasons to worry about Iranian financing of terror and the supply of heavy munitions directed against Israel, it has shown a capacity to destroy significant swaths of Lebanon, Gaza, and the West Bank to cause its enemies to think hard about further attacks.
Officials and activists on both sides of the American-Israel divide are speaking about what will come after the controversy about the agreement, either with the greater probability of it surviving Congressional criticism or the lesser probability of Congress overcoming a presidential veto.
Even though Barack Obama may be hard pressed to express anything like a concern with extremism that is Islamic in nature, realities have led him to express concerns with Iranian support for terror, and to send his airforce and military advisers against the Islamic State.
Here lies the opportunity for joint action, and keeping Bibi and Barack under the same tent. Both have come to support Egypt's campaign against Islamic extremists, and Saudi Arabia's campaign against Iran's clients in Yemen. The US has worked to bring Turkey along with respect to its own attacks against the Islamic State, while doing what it can to navigate the mine field of Turkey's issues with Kurds, who have been as successful as any of the fighters against the Islamic State.
The Middle East is not a playground for the innocent. It'll take some time to see how Barack Obama and his successor(s) operate in a place where all seem to be enemies of all, as well as occasional allies.
First up on the agenda for Obama's political maturity would be to recognize realities in history as well as the present, that Bibi is only doing what Winston did, and to assure that the US stays on the side of humanity rather than evil.