It's hard to predict the end result of a point of divergence that dates back more than 300 years. Without slaves certainly the economic development (and population growth) of the United States would have gone more slowly in the years leading to time of the American Civil War in our history. After that though they wouldn't have experienced the post Civil War dip in productivity, particularly in the south and they wouldn't have dealt with the social and economic burden of things like segregation and the resulting legacy of racial unrest.
So I think that hypothetical United States would have overtaken the real one in wealth by now. There would still be slums of course, people stuck at the bottom of the social ladder who can never work their way out, many of them hispanic, Asian or eastern european in descent. The labor shortage would compel the United States to open its doors to mass immigration earlier in its history.
It's hard to say what the music would be like without the invention of jazz or rock and roll. It would have taken the United States longer to give the vote to female citizens because that movement was an outgrowth of abolitionism but by now they'd have the vote and they might even have seen their first female president already.
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.