Actually, blues inspired jazz, rock, reggae, Hip-Hop, R&B. So without blues, all thoses style don't exist. Also Country music would be different. No Gospel music without black too. No Funk, no Soul, no Ska, no Disco, no Punk.
Interesting selection. Of course you're true, except for the fact that Jazz is actually a "black" style independent from Blues.
But look how much Blues there is still today in what is call "Rock", which is supposed to be the closest among current music styles. My statement was that this influence is very much watered down. Sure, you change its history if you change the past, but that prevents only few features.
It's the same problem as with many other WIs:
Things will be different, but there's no obvious indicator why it would
necessarily be that much different.
However, cultural and social matters are tricky.
It seems more plausible to argue Goebbels would have wanted his total war anyway even the class bully hadn't robbed his lollipop,
than to state Ligeti would have written the same works even if he had never listened to a jam session.
But there is hardly a way to tell whether it's true.
Although, on second thoughts:
Forget about the music for a while. Consider social changes inspired by black music:
To begin with, think of all the (actually) black musicians who had access to a different world through their performing; and think of the white people - eventually also in Europe - who had whatever distant contact to a black person only because that one was a singer.
Go on phantasizing from here ...