Everybody was waiting on the completion of the Yalta Conference where Roosevelt, Churchill and Stalin divided up Europe and condemned Eastern Europe (not one of the aggressor states) to half a century under the Russian yoke.
It all makes sense man ~ think of it this way ~ we didn't even need to land at Normandy. We had nukes coming up and if we'd waited a year we could have obliterated Germany in its entirity and saved hundreds of thousands of American and Allied troops lives.
We ended up not doing that, but there was, in hindsight, no reason for the US to have ever directly engaged, on the ground, with combat troops!
Till July, 1945 not a person in the world knew whether the nuke would actually work. It would have been the height of irresponsibility to build a war strategy based entirely on the success of an experimental weapons program.
Not to mention that with no Allied troops on the ground in Europe there would have been nothing to stop the Red Army from going to the Channel.
While we had nukes by mid-1945, we had very few nukes.