Assuming that by 1945 Germany has beaten the USSR and rules all of Europe and parts of North Africa/The Mid East.
The only option of winning for the USA is the Nuke. In late August two Nukes are dropped at Berlin and Hamburg. The US warns Germany that if it does not surrender (even conditionall) the US will continue.
As a result Germans are evacuated from all major cities into the countryside and production is shifted.
Now the factories are manned exclusively by Jews and British/American/Soviet/French prisoners of war.
New factories are build in Paris, Oslo, Warsaw, Vienna, Prague, Brussles and all the other major cites of Europe - these factories are manned by German workers.
So the next time the US nukes a German city it will kill tens of thousands of Jews and American and allied prisoners of war.
And to destroy German prodcution the newly build factories in occupied cities would have to be bombed.
Would the US nuke Paris, Prague, Vienna, Brsseles, Oslo and alle the other cites it wanted to liberate?
The US public would certainly not support this and would demand this to be stopped - also the US would turn the whole continent against it when nuking thouse cities.