Hi,
2) It's was a suprise attack. Even if it's a response to US economic sanction of June 1941, there were no declaration of war contrary to Europe, where UK and France declared officially war to Germany on september 3 , 1939 two days after Germany invasion of Poland.
3) The US where within it's right not to intervene. In the international order, there is no compulsion to do anything anyway ( even modern UN can only inflict sanction on a country, but cannot oblige a country to defend "international order" under it's banner.
To know if it's was or not a good thing is extremly debatable. On sure thing is taht you need a very strong reason to ask of your citizen to engage in war. As in war, people may lose theirs life. So as long as vital interest is not threaten, it's understable that President Roosvelt did not engage sooner.
4) It's showed to Hitler that France and the U.K were politically weak, and would not intervene as long as they are not directly threaten. The public opinion of this country were pacifists.
Chamberlin was wrong to trust him. He could have infer it from previous breaches of world war I agreement of not placing troop over the Rhine or from it's involvement in Spain's civil war of 36-39. However, Public opinion was there not ready to accept military intervention anyway.
