What question should I choose for my History Coursework? (A2)

I have to choose a question which examines a 100-year period, but it cannot overlap with either the cold war, Britain in 1906 - 51 or Nazi Germany. I really want to study American History,  but I can't go past 1945. I'm really struggling to think of a good question that covers 100 years and that I'll be able to write 3500 words for. Any suggestions would be greatly appreciated. Thanks!