Not to mention Hitler may have succeeded without US help.
not likely. the soviets had done most of the work by the time the yanks came over. it was actually the soviet union the country which defeated the nazis.
there's a case of discussion as to how much the USA's influence amounted to keep the soviets eastwards in europe after the war was over. perhaps without the USA, the Soviet Union would have kept a vast part of western europe under its control.