Okay, so WW2 is conducted and finishes as it does in real life.
Except for the fact that the Manhattan Project is a dismal failure, as are nuke programs of all other nations for a few more decades. So how does this play out? (BTW, Japan surrendered even though Hiroshima/Nagasaki weren't destroyed. The US didn't have to invade the main isles. The blockade did Japan in.)
So what would happen in the aftermath of WW2? Korea and Vietnam? Or would any of those wars happen?
What if Operation Unthinkable was enacted? As soon as WW2 ends, WW3 for all intents and purposes, begins. Even though the Allied Armies, Air Forces, and Navies were extremely large and of a great quality, isn't it true that at least with respect to sheer numbers, USSR had the slight edge? Again, only numerically.