What would have happened if Hitler had conquered Britain?
Hitler had a plan for the occupation; a long list of People they wanted to arrest and kill. 1 million British women was planned to be sent to Germany as wives. How serious it was is disputable. There would be lots of executions in any case.
King Edvard VII, would have been brought back and used as a puppet king, as Hitler liked him and vice verca. Germany would have taken her african colonies back, probably some of Britains as well. I am unsure if Britain would have been robbed of all their colonies. Probably not, judging from the French Peace treaty, which was very very mild. Hitler did not even institute a fascist regime there, as some People seem to think would have happened in the UK.
This would have never happened.
It was basically wartime propaganda by the British to sway international opinion and bring the US in on their side. While their war contribution was massive, and they were indeed in the backyard of a juggernaut alone for a period, there was never a chance of Hitler landing troops on the shores of England, and the British Empire had 25% of the worlds population and 30% of its landmass to draw resources from.
The Royal Navy was not going to let an invasion happen period.
Let's say it did however. The British Isles would quickly fall if a German Army established a beachhead and were well supplied. That's no small feat however. If a true emergency such as this happened, The Royal Navy could call home the majority of it's fleets and sink convoys coming from France and Norway with impunity, and the German Army would quickly run low on supplies and starve if they didn't force a capitulation in the opening days/weeks.
I believe that Roosevelt would get involved at this point, maybe not in the form of a war declaration, but possibly in a form of a ramped up lend lease program, or may cut if off completely over fears that the supplies will be taken by the Germans.
If the US did use this as a Casus Belli, a combined British and American fleet would utterly wreck any prospects of Hitler supplying his troops on the isles. The German Army would be unable to withdraw similarly to Dunkirk because they lack command of the seas, and while naval casualties would be large due to the Luftwaffe operating from France, the Allied Navies of the US, UK and Canada would indeed hold the line(UK could probably do this alone however).
Japan may see this as a good opportunity to attack the Allies in the Pacific, and after the German army in the UK is defeated, the war would progress almost normally, despite Hitler having a bloody nose and the outrage over Pearl Harbor not driving The Americans into such a rage.
A : Adolf Hitler would not have conquered England because England had much more resources including man power at its colonies.
However, this does not mean that there was no effect of Adolf Hitler on England. Decolonization from all the Asian country was definitely not a willful act but was forced by the circumstances created by Adolf Hitler. From that perception Adolf Hitler caused heavy and permanent damage to England. Also the image of the most powerful country in Europe got proved wrong.
Well, I don't know what would have happened, really... but he obviously stopped because the witches cast a spell on him, as depicted in this article.