Atticus says that it is a sin to kill a mockingbird because all they do is sing pretty songs to us. Well the whole point was that they are innocent and don't harm anyone in any way and it would be a sin to kill a harmless creature.
Atticus says not to kill a mockingbird because a mockingbird is innocent and has done nothing to harm anybody. This relates to Tom's trial because Tom has only done things to help people and he could be completely innocent but racism will hold him from a fair trial.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.