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There is a view that the West had some ability to prevent Stalin running Poland and Eastern Europe.
When I look at the map I tend to doubt it.
I can kind of guess a few scenarios but all seem unlikely
1) The Soviet Union does a lot worse, perhaps a withdrawal from Stalingrad in time and a better show at Kursk (I tend to assume this is more likely with Hitler dropping dead but still unlikely)
2) A huge effort at a D Day in 1943- and a willingness to accept the kind of casualties the USSR suffered.
3) Something clever and lucky in the South, either a better use of Italy's swapping sides and a lot of luck or perhaps landing in the South of France in 1943.
4) The suspension of the bombing offensive in 1944 to offer support to the Warsaw uprising.
My reading is that the way Stalin had behaved in Poland 1939-41 meant that any legitimate Polish government would be deeply anti Soviet and that no Soviet government would have tolerated that. The West was too invested in Poland to accept that.