I'm sure this has been broached in this forum before, but I am too lazy to look for such a thread

so I will just do this instead. So, having read Turtledove's book, I must say I found the idea of uber - Deutschland/Gross Deutsches Reich intriguing, although the typical, bland/I - can't - really - be - bothered - to - care approach to his writing was poor. I wondered, however, how might a scenario like this be possible, that is, triumphant Reich that strides the globe?
*Note some important changes that I am making right now:
Germany made Ukraine a fascist ally, as well as Lithuania and Estonia; otherwise, most of western Russia is part of the Fatherland. Central Asian republics are German allies, and a white Russia rump in Siberia (which is too weak to be a danger to anyone) is nominally German - allied.
*Turtledove goes WAY overboard on the Axis massacres: in the area of hundreds of millions of people being killed off. I am going to say, this is ridiculously impossible and so let us just ignore that bit of trash.
Germany got her WWI colonies back. Developed them post war as she saw fit, I don't have a clue what she did with them.
I forget when US (and Canada) are wrecked. Any thoughts on how this scenario might pan out?