Poland gives up Dantzig to buy time or Hitler decide to waite for that.
The attack on Poland still happens, in spring 1941. Because Germany haven´t mobilised for war since September 1939, its army is more comparable to what it was historically in spring-summer 1940, except in terms of technology.
The following plan is no major operation for 1942, followed by a blitzkrieg in 1943, most likely in spring. The following campaign being planned to lasting until 1945 at the most.
The Anglo-French alliance declares war, this time an offensive is launched against the Rhineland but the Westwall have been completed, the allies gives up easily after the first bloodbaths. The Soviet-Union mobilises, Stalin begin planning total war.
In summer 1941, Hitler and his generals wonder what they are going to do against France while an offensive is prepared, in autumn 1941 the offensive begins.
The French army is better off but so is the German army those Panzers have better armour and cannons now. Situation is, somewhat, a mixe of historical Operation Barbarossa and Case Yellow. France is defeated.
Roosevelt lost in the 1940 elections without France being beaten back then, the new president is not the interventionist Roosevelt was and doesn´t promise to do his best to join the UK in a war.
Even if Churchill still comes to power, he´ll most likely negociate an end to the war, before 1942.
Then what? With the UK out, Stalin knows very well what Hitler have planned for in the spring of 1942, now that war mobilisation have advanced the time for his offensive on the Soviet-Union.
Germany is significantly weaker, in total forces, Hitler also demobilises the economy as the war with the Anglo-French is concluded, Stalin does the opposite.
Because of the German demobilisation and possibly because of climatic conditions, ITTL Barbarossa may come a few weeks later or not.
Disaster strikes in the summer of 1942, Germany fully mobilises its industry but the Soviet-Union mobilises its greater industry, the following 2 years see the complete defeat of Germany and its allies. On the front, it is a massacre and a brutal war of destruction.
Occupying the whole of Germany is too much for the Soviet-Union, because Germany and its allies have over half the population of the Soviet-Union, instead Stalin makes sure central and eastern europe is communist and later, instaures a governement in ITTL west-germany which is a pro-soviet neutral.
Later, the Soviet-Union expands to obtaining acess to the Indian Ocean and the Mediterranean, forces both the Japanese and Chinese into territorial concessions. The UK may or may not try another war, most possibly not, since they would fight their victor´s victors.
The United States might leave isolationism in the name of anti-communism ITTL but the cold war would be far lesser up to the 1960s or even 1970s.