If Japan never attacks pearl harbour, they may well attack the USSR. However neither the soviets nor the japanese had the ressources available in 1941/1942, for major fighting in the far east. Also the japanese lacked a competent tank force, and the supplies to create and sustain one. They maybe reach Kharbarovsk, but thats the farest they can advance. The USSR had quite a lot of border forces in the east, and the civilian population had a high war spirit.
On the german-soviet front, there are rather few changes. No land-lease means the soviets forces are a bit less mobile, but the effect of american land lease was very minor to the course of the war. And the soviets didn't have to send many forces to fight the japanese (as allready mentioned their far eastern force was allways quite strong). Its likely that the red armys advance would be a bit slower, but by 1945 (at latest) all of the Soviet Union is free, and by mid to late 1946, the red flag flies over Berlin. I doubt that the nazis would do any better (by significant means) than OTL, let alone reaching a stalemate, considering these numbers.
https://qph.fs.quoracdn.net/main-qimg-980ab93832a8719d3a6d3ac0937a26ee
Now, without US help, the Allies (by this point only britain and its dominions) can not hope to land in Normandy or southern France. Without operation torch, the war in africa is longer and way more costly for the british. Even a landing in sicilly would be very hard, not to speak about further advances. So after Berlin fell and the wehrmacht lines collapse, the USSR moves on to liberate all of europe. If they are very lucky the british can seize southern Italy and most of France in the wake of total german defeat. In any case, eastern europe, along with all of Germany, Denmark, Greece, Austria, Benelux, and maybe France, Italy and Norway are red after the war.
As V-E day comes the USSR is able to move masses of forces to the far east. Think about operation august storm on steroids. Japanese forces are crushed and the red army liberates most of northern China, all of Korea and eventually, though inevitably, all of mainland Japan. Maybe they would even get the east indies and south-east asia (still occupied by the japanese when they surrendered, OTL).
The post war world would be quite different than OTL, and pretty red. If France and Italy didn't become communist after ebing liberated by the soviets, they would likely do in the lost war period (even when the US tried to supress them in OTL, with CIA, funding, marshall plan and Nato, they allmost won).
If the US stays isolationist after the war is debatable, but likely in my opinion. They have no presence abroad and no reason to take the risk. Britain may form an anti-communist bloc, with its few remaining allies, but they would not nearly be a match for the communists. De-collonization (even without communist France prior) would see most of the third world go communist or at least pro-soviet (without tge strong capitalist bloc, lead by the US). Britain becomes isolated, the CPGB gains in strengh, and in the early 70s, Great Britain becomes communist aswell.