Could the US have attacked Russia at the end of World War 2?

The US could probably have defeated Russia at the end of WW2, but at a cost that would not have made it worth it - and they had after all been allies during the war. The US had, though being in the winning side, suffered major blows. Their focus was on rebuilding their own military, caring for the veterans and the families of those lost, as well as rebuilding the war-torn Europe through the Marshall plan.

The US and Russia had fought together during WW2, and a war between the victors would not have been a good idea for either of them. Mind you, they also had respect for one another after being on the same side during the war.

Relations between the US and Russia worsened when they both wanted Europe to ally with them, resulting in the Cold War, where Northern and Western Europe, as well as much of the south, decided to become allies of the US, while Russia more or less forced Eastern Europe to cooperate with them and formed the Soviet Union.

So: The US could have, but they had no reason to attack what had been an ally, and Russia were strong enough to deliver pretty hard blows to the US.