Very briefly:

• The US atomic stockpile was VERY small after World War II. Total assembled-and-ready-to-go weapons in early 1947 was likely zero. They had fuel for several dozen weapons of World War II size and yield, and would have required using bases very close to the USSR to deliver them. This doesn't mean they couldn't have done it, but it wasn't as much of a "knockout" weapon as it would later become.

• The Red Army was extremely large and seasoned compared to the US Army. The US's European allies were depleted and in a bad place economically. The US could imagine trying to win such a war itself, but it would be ugly, rough, and come at great costs. You can imagine it as World War II-style fighting with an occasional atomic bomb going off. That's ugly no matter how you splice it.

• It would have been tremendously unpopular domestically (the US citizenry was tired of war, the emphasis was entirely on demobilization) and internationally (the idea that the US would unilaterally try to use its new weapons to forcibly "liberate" enemies was already feared by many in Europe). This would especially be the case if the US used its atomic bombs as it had in Japan (primarily against civilians), especially lacking an unquestioned casus belli.

• The US was, while suspicious of the USSR, committed to trying to find ways to use the new United Nations as a way of preventing future war. This involved many honest attempts at deliberations and negotiations (including negotiations over whether atomic bombs should be banned). The UN would certainly not have approved of the US starting an aggressive war against the USSR.

• The fact that the Western Europeans would not have approved of this makes it also very hard to imagine how this would have worked, given that Western Europe would have had to be the "springboard" for any US offensive (even atomic) into the USSR. Just a total non-starter idea.

Thank you for your answer☺️