The only way to avoid a US entry into the war is to avoid attacking Pearl Harbor and the Philippines. If Japan had held out 2 more years Philippines should have been an independent state, making it easier to attack and not involve the USA.
The problem is Japan is low on Oil they can continue for about another year in offensive operations. That's enough time to take Indonesia, the US Congress will not approve a declaration of war over Indonesia. Indonesia's oil would give Japan the resources it needs.
Okay since Japan never attacks Pearl Harbor, the USA never declares war on Japan, Germany and Italy never declare war on the USA. The USA is at least for the foreseeable future out of the war. FDR would continue making preparations as he wants war. That probably means a modest ship building program, modest army and marine build up. He'd use the new assets to shore up Hawaii, Alaska, Philippines, Puerto Rico, and the Bahamas. He would concentrate on preparing defenses in the Pacific, Caribbean and elsewhere. He would also establish US bases on the various British holdings including the allowed airbases acquired in the Destroyers for Bases deal in 1940. Lend-Lease will continue for Russia, France, Britain, and other allied nations (Turkey for example). If Japan invades an independent Philippines later in the war then lend-lease would be extended to the Philippines.
What happens in Europe. Mostly the war between Germany and Russia continue as OTL, Germany has early gains in 41 but the winter of 41 sees them lose ground. 42 sees another German offensive which like in 41 does not achieve its objectives, the Soviet war time economy has now outpaced Germany's. To put it plainly Germany is in deep doo doo. There will be no western democracies. Britain lacks the resources to do a D-Day style invasion in 44 like was OTL, they will continue to bomb and maintain naval dominance which ultimately will help Russia defeat Germany but mainland Europe is going to fall.
From France all the way to the Pacific Ocean the Union of Soviet Socialist Republic will become the largest empire ever seen on Earth controlling Europe, the Middle East, and their OTL holdings in Asia minus Japan's holdings.
Japan no longer distracted by America manages to conquer China, Manchuria, Korea, Vietnam, Burma, Indonesia and the islands at the height of the Empire of Japan. They avoid India and Australia. They sue for peace with Britain, and it is accepted. (They were already at peace with Russia).
Britain keeps its holdings in the Americas, Australia, New Zealand, South Africa, India. Much of the Commonwealth though desires to be independent and with the threat of the Union of Soviet Socialist Republic and Empire of Japan some like Australia could actually join the United States, this would be a peaceful transfer of power. To create a counterbalance to USSR, the USA probably seeks alliances and greater investments in Mexico, Central America and South America, it might even offer folks opportunities to join the United States, some will take and others will not.
No United Nations arises.