Phantom Blood takes place entirely in England with the Joestar and Brando families explicitly being British people, but you can make Speedwagon and Zeppeli whatever you want. Erina as well, to be honest.
Battle Tendency is about a British-American and his Italian friend fighting South American gods and Nazis. The Pillar Men got ya covered here, but you could make Stroheim Brazilian if you really had to.
Stardust Crusaders is easy, because Avdol is Egyptian, Polnareff can be black, and Kakyoin's just some weird guy who could be from anywhere. And you could change Iggy's breed.
Diamond is Unbreakable is pretty much impossible since everyone (except MAYBE Kira and Okuyasu's family) has to be Japanese.
Vento Aureo? Easy. Make Diavolo's organization a bit more global (the names can easily be codenames) and you can change anybody to anything.
Stone Ocean is every bit as easy. Our protagonist is half Japanese but with British/American ancestors (and the Pucci brothers are mulatto because backstory) but people like Ermes, Narsiso, and FF can be changed easily.
SBR? Make Lucy black and give Poco and Sandman more to do in the plot. Hell, make Mountain Tim black too. Or Johnny, even. The only ones you can't change are Gyro (Vatican assassin and all that) Diego (British douche) and Valentine (US President).
Have not read Jojolion.