If somehow, the Commonwealth forces manged to defeat Axis forces in Libya in early 1942...
I assume this means a complete defeat with capture of Tripoli.
what next for Allied forces?
French North Africa. It was full of "trimmers", and decisive Allied victory in Libya is a strong wind.
The Allies are not then in position to move into FNA in force... but organization for a pro-Allied coup d'état would soon be in full swing.
In OTL, a group of officials, generals, and business operators in FNA organized for such coup in late 1942. By the time of TORCH, they had enough muscle to seize control of Algiers in advance of the Allied landings (but not to hold it; Vichy regulars had much of it back by the time Allied troops moved in). They failed to get anywhere in Oran or Morocco. This group was
not part of De Gaulle's "Free France" organization. Their idea was to take over Algeria (then French national territory, not a colony), and be recognized by the Allies as the government of France with Giraud as theeir figurehead. (After which they would cut themselves lots of juicy deals.)
However, when TORCH came down, they had only been working on it a few months, didn't have enough troops, and not enough support. This was in large part due to the still-apparently-strong position of the Axis in Libya and Egypt: Rommel was retreating from El Alamein, but it wasn't clear he was permanently beaten. The Allies had to make a deal with Darlan to get the FNA authorities on side.
But if the Allies are standing on the border of Tunisia, ready to march in, and there are no Axis troops around... a lot more people will back the coup plot.
At the very least, alt-TORCH would be unopposed in November; quite possibly it could be moved up to September or August, and there would be no Tunisian campaign, of course.
This advances the Allied timetable in the Med by 7-9 months; not a small effect. The Axis of course does not lose an additional 300,000 men in North Africa, and the Allies (especially the U.S.) will not have forces ready any sooner.
By November, something like TORCH is possible, but where? Sicily, Sardinia, Greece, Crete, and the Dodecanese islands are possibilities.
Sicily is the nearest target, but is also the largest and most heavily defended. U.S. troops and most of the British troops available will be entirely green; it may be too much to try in say December 1942.
Crete is a smaller bite to take, and can be more effectively isolated from support, but it's further from air cover.
Greece is on the mainland with the German army, and very hard to cover in the air.
The Dodecanese are a little harder to reach and to cover than Crete, but an even smaller bite, and there are only Italians there.
Out of theater knock-ons include Australian divisions transferred to the Pacific five to six months earlier; these troops would not arrive in time to affect the Malaya or Burma campaigns, but would make a huge difference in the New Guinea campaign.
Australians could be posted on Guadalcanal and Tulagi, preventing the Japanese from landing there at all.