Bro if Germans had defeated Britains not started a war against Soviets. Then US would have been alone against 3 powers ie Italy,Germany and Japan. So they would have never taken the risk of fighting all 3 powers simultaneously. Hope you got my point bro.
After the attack on Pearl Harbor, there was no way USA was going to sit back. The war against Japanese would had still taken place with Manhattan project happening and the Atomic bomb being made.
Germany was doing well in the war as long as it was attacking neighboring land. The blitzkreig relied on air support, tanks and the foot soldiers. Without anyone of that, their strategy would collapse. USA's advantage was aircraft carriers and plus the allies were always technologically advance. Germany having nuclear bomb was speculative as Heisenberg was not making much gains as it was assumed.
The war would had continued.
Plus, Germany had little resources near the end of the war, they were running out. Even if the captured Britain and used there resources, Britain was quite big and the Germans would had needed time to manage the newly gain resources. Infact, even communicating from Britain would had been a massive task as there is water in between.
Anyways, USA and its carriers had an advantage. I think the German naval had like 1 or 2 carriers, while USA was sending a carrier upon carrier towards Japan.
Anyways, Heisenberg's bomb was no where near completion.
The only way Hitler would had won WW2 if they had capabilities to target USA which was quite far for them, or if Japan had the capabilities to go after USA.
Japan and UK were quite similar as they were defending from their land, but once the Atomic bomb came in, it was game over.