We were not the 'sole winners' of WWII. France, UK,Canada, Australia and the rest.
That depends on how you define "winner".
There's no real question that Germany and Japan lost (eventually); But identifying who won is not so simple. The USA and USSR won; Both became superpowers, with the latter gaining huge areas of territory in Eastern Europe.
But it's dubious to suggest that the UK and France won; They entered the war with the goal of restoring Polish sovereignty, and completely failed to achieve that goal; Poland was divided up between the Third Reich and the USSR, and the defeat of the former handed their share to the latter, and neither the Poles themselves, nor the Poms and the French, could do much about it.
The British Empire collapsed post-War; Even the most devoted of the dominions moved further away from the UK, and towards the newly superpowerful USA.
Arguably, the European Theatre saw three wars in rapid succesion; Germany (secure behind a non-aggression pact with the USSR) fought England and France for territorial domination in a war in which the USA was steadfastly neutral. The war lasted from 1939 until Germany won it, in June of 1940, with the fall of France and the withdrawal of British forces from mainland Europe.
There was then an uneasy peace in the European Theatre, until the launch of a new war between Germany and the USSR a year later.
The German-Soviet war was to last until May of 1945, when the USSR finally defeated Germany.
A third war was launched in July of 1943, when the British Empire and the USA, now allies, invaded Italy, and then a year later German occupied France; They cooperated with the USSR against the common enemy, but other than the defeat of Germany, they shared few goals with Stalin.
We tend to group these three European wars into a single entity, largely because the belligerents were engaged in hostilities in other regions throughout - Notably in North Africa, and in Naval warfare in the Atlantic, Arctic, and Mediterranean, as well as being allied to the belligerents in the 1936-1945 Pacific and South East Asian war between Japanese Empire and China, the various colonial administrations and posessions of the European nations, and (after the Japanese expansion of the war through her attack on Pearl Harbor at the end of 1941) the USA.
By the time the USA entered the war in the Pacific, it had been raging for five years; And by the time the first US servicemen arrived in mainland Europe*, the western part of the continent had been technically at war for four years, and "at peace" under Axis domination for three (with no in-theatre combat between ground forces in the west, though the air and sea wars of course continued throughout).
The simple narrative of the war starting with the USA being hit by a cowardly surprise attack, and then defeating Germany and Japan with a little help from some of her allies, is strictly for Hollywood.
I am tempted to say that nobody would take such a simplistic analysis seriously; But then I recall that most Americans can't find Poland on a clearly labelled map of Eastern Europe, and wonder if I am being far too optimistic.
*Obviously excluding PoWs and downed airmen who were hors de combat