I can easily think of one outcome in November 1940 that would lead the British to sue for peace with Hitler. Roosevelt loses the 1940 Election to Wendell Wilkie.
Wilkie might not be an isolationist, but he was nowhere near the friend to Churchill or the UK that Roosevelt was. Wilkie could represent much more onerous terms for the US to help the UK and for the US to behave in a much more self-interested manner as opposed to behaving according to Wilsonian morality as Roosevelt and Churchill did. In short, Wilkie might think more like Theodore Roosevelt, fighting as an American rather than an ally. And that might dismay a number of people in the UK, key people who would carry the day for the peace Herr Hitler was offering rather than for fighting on.
And lets face it, the Republican Party in the US represented the elements of the American business community such as Prescott Bush and Allan Dulles who favored accomodation and doing business with Nazi Germany rather than war with Nazi Germany. The election of a Republican candidate would thus be very dismaying to many in Churchill's coaliton--probably enough to cause Mr. Churchill to lose a vote of confidence on a war that would likely cost the UK it's empire.
The most immediate results of this peace agreement are going to be felt in the Middle East. The Palestinian Jewish Yishuv will revolt IMMEDIATELY against British occupation forces in Palestine as soon as they get reliable word of British capitulation--with the help of Free French forces in Syria who have been smuggling arms to the Haganah all along. For them, it's now War to the Knife,
and a matter of neutralizing the British forces, the Arab Legion of Transjordan and then seizing the Sinai and using the Suez Canal as a defense line at least until the Soviet Army can reinforce them from the Caucasus within a few months over difficult, but not impossible logistics. The size of the units involved is relatively small and the stakes involved for the Russians to hold Rommel at Suez rather than at either Kirkuk or Yerevan are well worth the military effort involved in getting to Suez, Haifa, Beirut and Latakia even with Moscow threatened, but the lines against Moscow starting to hold.
For all his much vaunted caution, this is Stalin's big chance to permanently break free of Anglo-and now Anglo-American containment lines barring the USSR from the Mediteranen and Indian Oceans in a way that will make it impossible for the US and UK to demand a return to the status quo ante. Iraq is now in a power vacuum. As is Iran, Saudi Arabia, the Persian Gulf Sheikhdoms, Yemen, Abbysinia and even British India. All are now guarded by small numbers of now belligerent British troops.
And the US is still in the process of sorting out it's policy toward it's erstwhile closest ally. Does the incoming Republican Administration follow suit with Great Britain and align with Hitler's "new order" against "godless Communism:?"
Or follow a more Rooseveltian policy of fighting on with the USSR against fascism; a policy which will now involve the truly distasteful task of moving to pull the British dominions away from the mother country, and in the case of Canada and the West Indies, perhaps even annexing them and the other European colonies in the Western Hemisphere the response to such a security threat that the Monroe Doctrine demands. If the US is to construe fascism as a security threat at all.