You are correct. The 1945 Red Army would have been a very tough fight. And with the war still going against Japan, and the looming prospect of a very costly invasion of the home islands, the American people were going to have a hard time accepting those losses.
Under those circumstances, there was absolutely no way the American people would have supported turning on a recent ally, and paying the costs necessary to defeat them.
Patton may have been correct in immediately recognizing that the USSR was an enemy. But for practical and political reasons, what he proposed was not possible.
Red Army sacrificed a lot of soldiers. They lost 100,000 just taking Berlin.
Of course one could understand their motivation, when it came to fighting Nazis, but would that same motivation extend when it came to fighting the Western Allies?