Is this from the novel China Dolls? If so, then I believe it means that if Dorothy Toy and Paul Wing had been white (Caucasian) instead of Asian American things would have been different because they may have been famous throughout America instead of just in Asian American nightclubs.. Or if it had been today, meaning 2014 rather than many years ago, they may have been famous throughout America instead of just Asian American nightclubs.

The past perfect is used here to denote a hypothetical situation. If it had been white : something is not white and therefore something did not happen or was not the way it worked. BUT: If it had been white, the situation could have been different. The same with "today". Because it was not today, something did not happen (or happened), which would be different if it were today.