According to wikipedia the US had monopoly of nuclear weapons at the beginning of the cold war. From 1947 to late August 1948, when the soviets achieved their first ever nuclear weapon"First Lightning" to the world.
I don't really grasp why the US didn't use their advantage really early in this conflict, forcing reddition on the URSS. Surely, some thought that they should: "drop a few bombs to terrorize the ennemy"? It feels to me that the US could have cut short this war.
Granted a lot of parameters could be taken into account. Such as the Marshall plan was probably the first objectif, ethics clashes on dropping nuclear bombs, fear of another war... Or maybe I'm just missing something like the actual start of this war begin with the escalation in 1953, and before that it was more of a discontent between the two parties.
PS: Sorry for any grammatical/Lexical mistakes in my text.
You might be interested in this older answer from /u/Restricteddata on Immediately after World War Two, when the USA was the only atomic power, did any American officials consider a preemptive war on the USSR to prevent them from acquiring the bomb? It's a good summary of the reasons the US never really considered it.