Let's not forget Harold-Sulu played by John Cho in the 2009 movie is of Korean decent. Allegedly Abrams was concerned about the ethnicity of the character but George Takei explained that Sulu was meant to represent all Asian cultures in StarFleet.
Patrick Stewart playing a frenchman a lot of effort was put in to making Picard's heritage apart of his character. With Keiko O'Brien, Hoshi Sato, Harry Kim and even Sulu no effort was brought in to make the culture these of these characters apart of who they were. Like TPTB decided we need diversity on our show. Doesn't matter the actors ethnicity just cast them as anything. I mean it really is as simple as renaming them all. While it is the 22-24th century and all we don't see other characters waving their heritage and ethnicity in the audience faces so I guess it didn't matter to the show runners.
Riker for instance is American but he's not waving the flag and show boating American awesomeness.
Trip Tucker is form Florida and aside from his accent you wouldn't think twice about where he's from.
Sisko is African American, and the only hint to his ethnicity is the fact his family owns a Creole Kitchen. Meaning like Trip he's from the US's South.
When it comes to Asian actors however there is a self-conscious inclination for ensure races are being accurately depicted. Not a problem really, as long as their is no insults or parody of a culture. Look at Disney's Mulan. Majority of the voice actors are of Non Chinese decent. Most are Japanese or Korean actors. I suppose finding a lot of Chinese voice actors was difficult for Disney, so they out sourced to other Asian actors, and they did a good job and a lot of people like Mulan