Funny thing is - it DID just end in all the rest of the world. Only in the United States are the descendants of slaves still reviled by a significant portion of the former slave holders.
Only a small percentage of all the slaves transported from Africa to the New World were destined for the US. Brazil got far more slaves than the US did. Brazil has no serious race problem, do they? Maybe you can point to the history of SJW's in Brazil struggling to keep the black man on the plantations? No? Didn't think so.
YES, SJW'S CONTRIBUTE TO THE PROBLEM!!
Well you could blame US race relationions on a SJW phenomena that has only been around for 10-20 years, or you could blame it on a country which had to fight a civil war with the south to eliminate slavery, had another massive political fight with the south to eliminate institutional racism, and still has legislators and government officials actively trying to suppress minority voters.
Yeah, I guess it's totally the SJWs' fault*...
* Yes I realize you said "contribute" not "cause" but racism is heavily entrenched in US society (and many other societies). SJWs are guilty of suppressing some legitimate speech, but not of causing racism.