re: How would America be different today without history of slavery?

Hell of a lot better.

Rock and roll music would not have developed anywhere close to the way it did.

All your major early stars were either heavily influenced by black American music or were black.

The Rolling Stones, The Beatles, Led Zeppelin (especially), Pink Floyd, Little Richard, Chuck Berry, Elvis, Fats Domino, etc.

Without the R&B, gospel, etc. of blacks in the American south, none of that would have happened. We might still be listening to Perry Como and ditties like "How Much is that Doggy in the Window."

AA descendants would instead bitch about not being invited to America, where all the white men got to claim while leaving them behind, and ensure they receive reparations