Given a chance would you kill baby Hitler?

[Anomalocaris]

But it was Hitler burning the last bridges by declaring war on the USA. On december 11th 1941. The only war he ever declared instead of simply attacking.

Hitler lost the war when his troops fired the first shots.  He thought he was fighting an old style 19th Century war instead of a 20th Century war.  He was a good public speaker and he had a lot of charisma but he was an idiot when it came to warfare.  He had no real allies.  His base of operations was too small and he couldn't defend it.  He didn't have a navy or an air force.  He didn't have any useful weapon systems and he couldn't support his troops in the field.  He couldn't even invade England.  Plus his agenda of conquering the
world and killing "undesirables" eliminated him from getting any allies.  That's not a very good and appealing political agenda.  And he had no fifth columnists in other countries to create havoc.  It's also why Japan and Italy were so easily defeated although Japan did have a navy.  

It's interesting that before the war the US knew as early as the 1920s it would fight Japan.  And England thought that its war time enemy would be the US instead of Germany.

Actually, no.  Britain's national policy from 1918 onwards was while war with the US was unlikely, it nonetheless must proactively prevented any serious conflict with the US literally at all degree of appeasement necessary.   While Britain was still a real global military power, Britain accepted all sorts of American demands in the hopes of making America realize Britain would voluntarily weaken herself and deprive herself of the ability to wage war effectively against America in the hopes that America would not consider war with Britain necessary to gain its own ends in the case of dispute.  Britain's policy of appeasement literally started with the US, not with Germany.

That is the point those who scream "appeasement" at the slightest hint of rational compromise prefer no one remembers.  For Britain such compromises was indeed rational.