Usually the only way to stop this strategy is by sending planes via UK to Leningrad so Russia can transform them into Russian units. Also if Germany makes a mistake and leaves no fighters in Berlin you have to make him pay with SBRs. Also if you can do this, use the 12 IPC bonus in the Middle East so Germany has to waste more time trying to control that.
But I have found that you can make the battle a lot more interesting by also building artillery with Russia in large amounts to create a dead zone, if Germany is foolish and sends it’s infantry forward too soon the Artillery bonus plus the converted fighters will make them think twice about pushing too fast, allowing the US more time to mount an invasion on fortress Europe.
But that does not mean this strategy is fool proof, you usually have to hope for a German mistake for you to get the upper hand, but playing this way definitely makes Germany have to play nearly flawless in order to succeed before the US becomes a threat.