Agreed. The US was weary of war and the US was near broke. However, unlike 4.5 years of war with both the Nazis and Imperial Japan, IF we had a couple nukes and could reasonably convince the Soviets we had even more, a 1945-1946 war would have been very short. Perhaps by the end of 1945 in some alternative timeline. As it was, the US didn't have the bombs yet it did have too many commie sympathizers in government and academia. Ergo, I think everything worked out as best it could have at the time.
War is bad for everyone. Even the conquerors. It's why it should always be a last resort much like using a handgun or AK-47 in self-defense.
Roosevelt, then Truman, knew Stalin was a murderous lying asshole who could not be trusted. They had to balance the Soviet threat against a revolt of their own war-weary citizens.
I am not even sure nuking Moscow would have been possible in 1946. Japan's air defenses were non-existent in 1945. This was the era before ICBMs - getting a B-29 through one thousand miles of heavily defended Soviet air space - and back - seems unrealistic.
Japan had no counterstrike capability in 1945 -
an attempted American first strike nuclear attack on Moscow would have made us a rogue nation in the framework of international law and norms, and world have immediately invited a counterstrike on western Europe by the Red Army, which at that time was the world's largest and most battle tested army.
Summing up, a USA first strike in 1946 would have been foolish , unrealistic, disastrous