So Germany has annexed Austria, the Czech republic, and made a satellite out of Slovakia. Her army has expanded, the first jet is about to be tested, new technologies are on the horizon, and the UK/France are on the verge or war. Suddenly Hitler dies (insert reason here).
Plausible reason: the German officer corps, despite their general anti-Pole feelings, are wary to stage a general conflict about Poland, when they realize that Hitler is not out for a sensible compromise to return the "rightful" 1914 borders to the Fatherland, but wants to risk everything to build a mad Lebensraum garden in whole Poland. ITTL they get a bit more spine and a couple butterflies that put anti-Nazi conspirators out of key positions in the Heer hierarchy during 1939 do not occur, the old 1938 coup plans and connections are reactivated, the Heer stage a successful anti-Nazi coup in late August 1939. Plans to do so existed, the above OTL butterflies wrecked them.
An Heer junta takes over, purges the Nazis, enacts a "controlled" conservative democratic restoration under a constitutional Hohenzollern monarchy: civil rights are restored, Conservative, Liberal, and Christian Democratic parties and trade unions are legalized (Nazis and Commies are banned), SPD and socialist trade unions may or may not be legalized initially but eventually they are, a modified Weimar constitution and electoral system are established to restore a British-style constitutional monarchy, reinforce the executive, lower political fragmentation and instability, and ban extremist parties. The Wehrmacht carve for themselves the constitutional role of "overseers" and guardians of last instance of the political system, much like OTL Turkey. Louis Ferdinand becomes Kaiser. Federal autonomies are restored, even if borders of the Landers may be rearranged. Jews get civil rights back. Nazi leaders that survive the coup are court-martialed.
After it has stabilized, the new German government goes to Britain and France and bargains autonomy for the Czechs (either a Lander with special autnomy and minority rights, or a confederal association) in exchange for their support for sensible German claims in Poland. Their maximum program are the 1914 borders, their minimum one is Danzig, a land connection to East Prussia, and a revision of the Upper Silesian border. They also offer a naval limitation treaty to Britain, a reaffirmation of existing borders to France. Under the table, they make an offer to Britain: let us satisfy our last Versailles grievance and build a sphere of influence in Central/Eastern Europe by peaceful means, and we shall guard it against the Soviets and make not more trouble in Europe.
Since the democratic/monarchical restoration (and the end of anti-semitism) and the autonomy offers for Czechs give back Germany some of the goodwill that Hitler had burned with the betrayal of Munich, Britain is willing again to continue the appeasement strategy. The Munich II conference convenes to discuss the Polish borders problem. Eventually a compromise is reached about the return to Germany of Danzig, a strip of territory in southern West Prussia through Torun that connects Pomerania and East Prussia, and a slice of Upper Silesia according to the 1921 British-Italian proposal. Poland fumes and rages but eventually backs down and accepts the deal, rather than facing a war with Germany and maybe Russia alone.
At this point the TL faces a major divergence according to Stalin's and Japan's actions. Stalin may either be cowed by Western-German detente, or be roused to pre-emptive attack. Japan may be cowed too or go for its usual kamikaze expansionist rampage.
If they are cowed, relations between Germany and the Western powers gradually thaw and some kind of European cooperation may emerge fueled by economic concerns, Germany gradually becomes the economic giant of Europe and gets all the influence it wanted by peaceful means. Mussolini eventually builds a military good enough and attacks Yugoslavia in cooperation with Hungary and Croatian separatists, he gets Dalmatia and a satellite Croatia but Western powers and Germany join into containing him from further aggressions. Italy gradually democratizes when he dies. An indecisive war occurs between Hungary and Transylvania, the great powers enforce a settlement much like the Second Vienna Award. Russia may or may not fight a war with Japan to get Manchuria and intervene in China. If it does, UK, USA, and maybe Germany give support to anti-Japanese, anti-Communist Chinese. Hard to say how the three-way mess ensues. If Russia does not intervene, Japan exhausts itself fighting Chinese insurgency, eventually pulls out of China proper, but keeps Manchuria. Chinese Civil War occurs. Again, hard to say the outcome. Let's say Red North China and capitalist South China.
Russia follows a PRC course after Stalin dies. The USA still become a global powerhouse, but the world remains multipolar.
Alternatively, Stalin inteprets Western-German detente as a sign that the capitalist powers are closing on him, so he decides for pre-emptive attacks when he feels that the Red Army and Soviet industry are ready, sometime in 1942-43. A WWII much like our own occurs (but destruction is contained to Eastern Europe and the Middle East, and Stalinist atrocities in occupied territories occur instead of the Holocaust), with Stalin in the shoes of Hitler. Eastern Europe and the Middle East are overrun, but the European colation, supported by USA Land-Lease, stalemate the Red Army someplace in Poland & the Balkans and gradually beat it back. When the Euros get deep in Soviet territory, Russian generals stage an anti-Soviet coup and make a Brest-Litovsk peace.
Japan surely tries to exploit the situation, it may either backstab the Russians in RFE or the Anglo-French in South East Asia. if the former, it comes out of the peace table with Outer Manchuria, the Western powers don't want a Japanese China but Communism is the devil, so they give maximum support to GMD against the Communists and force Japan to pull out of China, but it keeps Manchuria and Inner Mongolia. If it goes south, events unfold just as OTL, the Soviet defeat is rather quicker since America joins the anti-Soviet coalition.
A multipolar world emerges with the USA and a federal continental EU (forged by wartime cooperation) as the main superpowers, Britain as the "strategic partrner" of either, capitalist China has its rise accelerated by several decades, Japan may be a great power if it was not beaten down to a USA vassal.
Culturally it is a rather different world where Communism, not fascism, is demonized, Stalin's atrocities are the archetype of absolute evil, and far right ideas remain respectable much longer.