If Britain had not entered the war a lot of things would have not happened as well. The Germans wouldn't have need to secure their Scandinavian steel supply so no Norwiegen invasion would have been nessesary. The Invasion of France (Assuming they still go through Belgium) would have ended a short bit sooner (No British Expeditary force). The Italians would have been able to retain Lybia and Ethiopia.
Assuming then that the Germans would still have decided to invaded the USSR in 1941 that would have probably have happened a few months sooner because they either wouldn't have needed to help the Italians in Greece or perhaps Italy might not have even invaded Greece. This earlier invasion would probably have allowed the Germans to advance farther faster because they wouldn't have needed to have entire Luftflotten (Air Fleets) covering Britain and the Mediterrean. Also the Germans would have had more material at their disposal and without Allied Bombings on Germany and occupied France lost material would be more easily replaced. The Luftwaffe would also have had many more planes and would have been able to retain the experienced cadre that were lost in the Battle of Britain and the Mediteranean. Also no Desert Fox!
Taking this into mind the Germans would have probably been able to have at least stepped foot in Moscow before winter would have set in. Assuming then that Soviets kept on fighting instead of surrendering it would have become more of a war of attrition then. The Soviets wouldn't have been able to recieve any lend lease (it did happen and help) and possibly not US lend lease. Thinking about it the framework for Lend Lease was only set up to help Britain and I doubt that Roosevelt would have gone out of the way to set up a system to help Communists.
I believe that the Germans would have then been strong enough to take on the Soviet Union. With a single front war the Germans would have been able to take European Russia. Granted the Russians had plenty of manpower but if there was no foriegn aid the Soviets wouldn't have been able to outproduce the Germans.
The Japanese would probably still gone to war with the US but there would probably have been no Pearl Harbor attack because that plan was inspired by an early WWII attack on an Italian navy port by a British carrier force that sunk several heavy ships. How the US would have fared in the Great Fleet battle scheme that the Japanese had I don't know, would probably be an even match between the capital ships but then the Japanese would have had the more experienced pilots. Also with no Britain as a launch point for Invasion a Europe first policy would have been impossible and the Atlantic would probably have just been a battle of sea lanes by the US against Uboats and a defensive action against US naval probes by the Kriegsmarines surface force. The Germans would probably have finished their aircraft carrier and their surface fleet would have not been damaged by the British as badly (especially from the lack of a Norwegian campaign). The Japanese also wouldn't have need to have forces in Burma or defending against Australia so they would have more forces to continue their war against China or to pit against the island hopping campaign of the Americans (supposing that was still the strategy chosen).
The Japanese-German/Italian Sea lanes would have remained open (Ethiopia to Japan) and who knows what material and technology would have been transfered.
American Military technologies wouldn't have advanced as far (except for their continuing nuclear program) the P 51 would never have been because it was designed for the British (because the US refused to build existing British war machines because they thought a British defeat was imminent)and even if it was built anyhow it would probably have still held on to those crappy Allison engines. American tank technology would probably have slowly advanced but wouldn't have benefited from the lessons learned by the British in North Africa, maybe the Grant tank would have been the pinnacle for a while.
As a side note the Spanish might have decided to join the war but who knows.

Anyhow my summary, Germans beat or stalemate USSR, Japan vs America is even match but probably US victory after invasion of Japan (I doubt that the B29 would have been developed if the Army Air Corps hadn't had the experince of bombing Germany) or it would have been a stalemate war with an eventual truce.

So yes German Europe, Italians still have small Empire and Japan vs US is only wildcard.