There's a difference between the will to make a superweapon... however long it takes... (USA/USSR...) and the will to make a superweapon... but it's gotta be ready in time for my B-day (Nazis)
Hitler and Co. simply didn't have the patience to wait, thus no atomic bombs and the Japanese had no effing clue as to what they were getting themselves into plus the rivalry between the army and navy was so bad they would probably have had 2 programs that were sabotaging one another. That's what I mean by not having the political will. Sure if the entire US boomer fleet was ISOT into Hamburg / Tokyo harbor in 1942 empty of people and with the launch codes next to the launch controls yeah the Nazis / Imperials would use them without the slightest hesitation or crisis of conscience but that's different from building a bomb and a delivery system that has little to no chance of being intercepted before it hits its target... that type of planning takes a very long view with a sustained political will rather than "Oooh! a-bombs will win the war!... whaddya mean it'll take 5 years!? Forget it! Go work on those big tanks I wanted a year ago!"
Well to be fair the Nazi's and the Japanese did not have time to build the bomb.
But what if the Nazi's had mangaed to win?
Two senerios, leading to two very differant hegemonies.
1. Nazis win. They develope nukes first, they have the best rockets, they have a very large percentage of world's economy, they decide it would be best for all concerned, ie the master race, if they only had nukes.
And they nuke anyone that builds a reactor.
2. Nazis win. They end up dominating Europe and Africa. Much of rest of world changes to work with them.
the US and UK get the bomb in the late 40s or early 50s and dedide as yo put that they are far superiour to the rest of the Nazi or nazi-friendly world. Either just tell Geramny that the new order is US/UK Hegemony and deal with it, which leads to war, or just launches a first strike on Germany.
Either way afterward the US/UK alliance is a nuclear hegemony that has a history that justifies not letting anyone else get the bomb.