"Whitewashing" is more about actual phenotypical appearance, than nationality.

Roberto's dark-skinned appearance (and his experience with how the world, Brazil specifically, viewed him because of it) was built in to the character from his earliest appearance. He was clearly meant to be Afro-Brazilian/Latino.

The creators even had characters, in-panel, in-universe directly harassing him because of it: https://worldofblackheroes.files.wordpress.com/2011/10/sunspot-origin.jpg

Though, Marvel has been recently depicting Sunspot with a lighter-skinned appearance, that isn't consistent with the in-universe experience the character clearly has had because of his "race," nor his depiction over the last 30+ years.