Coincidentally I just started reading "Night" by Elie Wiesel last night.
He described how angry he was with God for being silent.
It is easy to feel this way when you observe mothers and children being fed into the furnace, or witness a young child be hanged in front of the prisoners in order to "set an example"
So while the Americans did eventually show up, the time spent amid the horror and inhumanity must have seemed endless to these people.
I agree with the sentiments of the pope, that God must have had a mysterious plan and only He can understand why it was allowed to happen for so long.
May God bless the poor souls of all those who suffered, and who still do suffer.
I've come to the conclusion that, when we say "why doesn't God do something about x", he's calling us to act.
As you say, the Americans eventually showed up, and history is all about what it took to get us there, and what kept us from acting sooner. When you think in those terms, its actually scary, when you look around you at all the situations where God is apparently silent, knowing that it is "we" who have failed to act. Its not God who has failed judgement, its us.
I remember an old movie in which a group of believers were under attack, praying for help. A bunch of cowboys ride to their aid, laughing "they pray for God to help them, and all they're going to get is us".