Germans get the Afrikakorps butand they also get the some occupation forces that OTL were deployed as well ( some will have to guard borders that now remain ). They do lose the Italian support and probably a chunk of the minor allies as their borders have to be guarded. However a major constraint in the Russian campaign seems to have been logistics ( after the first surge ) and that is not affected by Italy staying out. The delay in date of the invasion also seems to have been mainly due to weather so probably would not change much.Well from my point of view the additional troops of the Afrikakorps are VERY dangerous for the Soviet Union.
Essentially you have a small Panzergruppe either for the HG Süd (Army Group South) HG Nord (Army Group North) or HG Mitte (Army Group Center).
I doubt that the additional troops would have been deployed in the Center because Hitler wasn't convinced that Moscow was an important strategic target.
In 41 he was pretty fond of quickly capturing Leningrad so the troops probably would have been deployed in the HG Nord.
This would have probably caused the Fall of Leningrad and then the interesting butterflies start in 42 with a lot of troops freed up....
Britain gains a lot , less troops needed in Africa, no losses in Greece and more importantly convoys through the Med are practical with little escort so no need to use the cape route. This frees up millions of tons of shipping and reduces the journey time a lot. It means Britain can reinforce the Far East ( which after IndoChina is occupied they wanted to do but lacked spare troops ). Given how the Japanese were tight at the limit and basically rolled 7's early on, this could easily give big butterflies ( Just not having Taranto will cause Pearl Harbor to be different at least ).