I think the litmus test would be very simple.
Suppose another country, let's say China, makes a big-budget star trek like series that becomes hugely popular across the world (not likely of course, but just assume it). In its universe, Chinese people are as predominant as American people seem to be in the 'star trek universe'. And of course, everyone speaks Chinese. Most other nationalities seem to be small minorities that pop up every now and then, even though there may be one of two 'token' members on the crew.
Would this bother you, as an American viewer of this series, even in the slightest? If the answer to that is yes, you may have an issue with the "over-representation of Chinese" in that series....
Of course, there's several ways to deal with that.
1) You are going to accept that it is only natural that if a series is produced in country x it will have an abundance of people from cultural background x, even when the series is supposed to play in the far future (the most rational response, imho)
2) You are going to complain on internet about the 'over representation of people from background x'
3) You simply refuse to watch it (the response I would expect from most Americans. Think soccer. Think American remakes of perfectly good original foreign movies that simply aren't "american" enough).