The soviet union and north america as well as others contributed well to WWII near the end.
However it was the British who brought them together, payed for the war and turned the tide with victory at the BOB. Without this the world would be firmly under nazi rule.
The soviets and north americans joined the war when attacked and had no probelms with hitlers ideals, and none would have fought without the British holding court.
The soviets and north amerians had no problems with sitting back while 6 million jews where slaughtered. The British payed for the European resistance, the soviets and their own war effort, so all used British equipment, once you buy something it belongs to you.
The British won the war with help from others, but mainly the courage, principles and driving force of the British.
The soviets and north americans would have handed over their blacks and jews in a second had Britain gone under, but tit never came to that, we can thank the British for that one.