Why is time not unlimited. The Allies were going to fight until the war was over whether it was 1945 or 1948. If the USA didn't join the fight in Europe then it would of taken time for the UK to build up its forces with those of the Commonwealth. This would of taken time (it took the US 3 years to build up its forces so it is feasible that it would of taken the Commonwealth a similar length of time). An invasion would of still been possible, the Commonwealth could produce as much as America as has already been said so supplies of equipment should of been alright. An invasion may of taken longer to develop and prepare for but it would of still occured. The Russians were forcing things in Europe because of their situation. Hitler would still of acted as irrationally as he did (which means he still might of declared war on America - similar way to how the US got involved in WW1) but this would of happened later. If the Balkans delay had still occured then Barbarossa would still of failed at the gates of Moscow and with the resultant plans going ahead the Germans would still of become bogged down in Russia. It would of taken longer for one of the sides to win (particularly the Russians). With Churchill animosity towards the Russians it is likely the borders would of been different post war had the result of the war been the same (borders further East).
Europe was dominated by Germany even with the US's industrial and manpower contributions until 1944, without the contribution Germany would of dominated for longer and I believe the Russians would of been unable to advance as fast (lack of American trucks).
Europe was dominated by Germany even with the US's industrial and manpower contributions until 1944, without the contribution Germany would of dominated for longer and I believe the Russians would of been unable to advance as fast (lack of American trucks).