As has been said, if Germany just fights the people it fought from 1939-1940, it can win. "Win", of course, would mean a negotiated peace because they sure as hell are not going to board the world's largest aircraft carrier.
Thats the thing: Even without war with the USSR, there's only so many forces Germany and the Axis can afford to deploy beyond Europe to combat the British Empire - the limiting factor is logistics, not total-force size.
As it was, historically: They were already near their maximum capabilities. Rommels drive towards the Suez Canal was done on a shoestring - limited by how much the Germans & Italians could ship through to Africa past the Royal Navy - and historically, the RN was actively winning the war/had won the war in the Mediterranean by the time of El Alamein in 1942.
The Royal Navy also had won the Battle of the Atlantic, while the RAF had conclusively demonstrated its capability to smash the Luftwaffe in the Battle of Britain. Britain & the Commonwealth was pretty much winning its fight against the Axis on its own in almost every combat theater beyond the immediate continent.
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Basically: Germany not going after the USSR will free up millions upon millions of soldiers & tons of equipment - but they will
mostly be confined to the Continent, since the Axis completely lacks the ability to deploy more than a
tiny fraction of them abroad to fight Britain's empire - and that capability would, just like historically, be progressively eroded away as the RN & RAF continues to chip away at the Italian Navy & Axis logistics (Fun Fact: Britain outproduced ALL the axis powers - Japan included - combined in naval vessels throughout WW2, the sole exception being fleet carriers - which had the war dragged into 1946 & 1947, Japan would have been hit with a Tsunami of British Carriers under construction - the UK's capability's are simply often overlooked because the USA outproduced
them several times over as well).
Basically then: Its very very unlikely Germany can achieve much more than it did historically against Britain's empire. They can drag out the African campaign a bit - but there is going to come a time when the Royal Navy achieves crushing superiority in the Mediterranean - leading to any Axis forces in Africa being strangled to death from lack of supplies.
After that: It just means Europe becomes untouchable to the UK - since without US Support, DDays not happening.
We end up with a Stalemate - Britain becomes a fortress on the coast of Europe, while the Axis & British forces skirmish in the Mediterranean/Africa - with little real strategic momentum achieved by either side there (Its almost inconceivable that the Axis would actually manage to reach Suez, even without war against the USSR due to the logistical-problems).
Unfortunately for Germany: The UK at the time (1941) was the world-leader in the atomic project. No US-Intervention means the merger of the British-US Projects doesn't go ahead - meaning Britain will continue to chip away on its own (rather than merging like it did historically, only to get double crossed and have to begin its own project again after WW2).
The USA will probably still beat the UK to the Atomic Bomb - but thats not going to do Germany any good at all, when the UK itself gets it - probably a bit sooner than 1952.
So.... stalemate, until Berlin disappears under a mushroom cloud. At which point, it becomes a British victory.
There's simply no way Germany & Italy can beat Britain, even when its on its own. The tide was already turning in the Atlantic, Africa & Mediterranean by the time Barbarossa happened - or had already decisively become a British victory (Battle of Britain).