On the other hand, if not for American/English involvement wouldn't there have been a good chance Russia would have been fighting a multi-front war? Sure, Russia could have taken Germany - could they have taken Germany AND Italy AND Japen if all three of them were focused on fighting Russia alone?
At the very least I think things would have gone on a lot longer and theres a very real chance Russia would have gotten beat.
Italy, along with Germany's Eastern allies (Romania, Hungary, Finland, etc), were not well used by the OKH, which is not to say they didn't make a difference. But generally, the Germans treated them as free reserve troops and put them in vital positions where they could be used better elsewhere, leading to the Soviets exploiting their weaknesses (the prime example being Operation Uranus, in which the Soviets completely wiped out the German allies surrounding Stalingrad and turned it into the disaster it was known for). Plus, they had a lot of internal problems, and switched sides pretty quickly when the pressure started to increase. It's unlikely they would be able to significantly turn the tide, though.
Japan is, well, complicated, especially since we didn't establish whether our hypothetical US is fighting a Pacific War or not. But with relation to the USSR, the Japanese had been having internal struggles with whether to head north into the Soviet Union (the preferred strategy of the IJA) or to head south to European colonies (the plan of the IJN). In 1939, both sides were about equally influential, when a border skirmish between the Red Army and the Kwatung Army turned into a full battle at Khalkin Gol. The Soviet commander was the famous Georgy Zhukov, who utilized the comparative Soviet advantage in armour to decisively defeat the Japanese forces there. This proved evidence enough to the Japanese that war with the Soviets would be unproductive, leading to the primacy of the IJN in determining policy and ultimately to the attacks on Pearl Harbour.
Now hypothetically our Japanese could decide to attack the Soviets anyway, but up until Barbarossa the Soviets had the Far East well defended with elite Siberian units that would have been more than capable of defeating pretty much anything the Japanese could throw their way (indeed, at the end of the war they conquered all of Manchuria in about a month and killed or captured well over 600,000 IJA troops). Now, it's worth mentioning that the transfer of these troops to the West was instrumental in the defense of Moscow and in turning the tide against the Germans, so a Japanese attack would significantly damage the USSR's ability to fight against the Wehrmacht, but they would basically be suicidally sacrificing themselves for the benefit of an ally of convenience halfway across the world. The Germans and Japanese were not close enough allies for even the irrational IJA to justify such an action, so chances are the IJN would still maintain control.
So to go on a little tangent, the IJN could hypothetically have continued from here in two ways; they could have avoided the American supported Philippines entirely and went through French Indochina to attack European colonies, or they could have attacked the Philippines, but tried to limit the war so as to avoid a total war with the industrial might of the USA. In the first case, Japanese supply lines would be hampered, but they could have probably managed to beat the European colonial forces in most of Southeast Asia on their own and used the oil from the Dutch East Indies to fuel further expansion. Roosevelt, while very much in favour of war, would have a tricky time justifying American intervention to rescue European colonialism, and even if he brought the US to war anyway it wouldn't be the largely unified US that was willing to fight bloody battle after bloody battle to get unconditional surrender from Japan. That likely wouldn't even be the case if the Philippines were attacked so long as the Japanese were very cautious, kept the war fairly limited, and treated American prisoners well. Under those circumstances, Roosevelt would have a very hard time convincing the American public to support the kind of war needed to fully reign in the Japanese Empire, and even without Pearl Harbour the USN wouldn't be really capable of projecting into East Asia against the Japanese until late 1942 at the earliest, so he wouldn't even have much to show for sticking in the war as opposed to accepting a more even handed peace agreement.
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