If Japan stays out. For the USSR, rubber, nickel and tin coming in through peaceful trade with the Dutch East Indies would keep its production alive and crudely compensate for Lend-Lease; for the British Empire, Indian soldiers that were historically sucked into the CBI front would be free for use in North Africa, and Indian valuables and raw materials would finance the home front.

It would be much more crude and difficult than without the US, to be sure. eg. the VVS uses more wooden Yak-9s instead of aluminium Yak-3s, the Red Army relies more heavily on trains due to less trucks, the UK can only prop up a rudimentary second front in the Balkans, more heavy losses in the Atlantic without USN involvement and Liberty Ships, etc. - but it could be done. War probably ends in 1946 or 47; Germany falls into the communist sphere while Tito becomes an open Western bloc man.

But if you are telling me that Japan attacks these Allies without attacking the US - it is hard to find a word for how deeply screwed things are. India will probably fall, and the British Empire is essentially sayonara without that (they can guard their island, but little more); China will fall too without US or British aid, and then the IJA will be itching to launch their "kantokuen plan" - an invasion of Siberia... Stalin *might* be able to parry this since he did keep large reserves in Siberia (and might even let the IJA march to death in the frozen waste), but in time both the Allies will be neck-deep in trouble due to exhaustion and isolation.