I've encountered an answer in which this exact phrasing was used (among others).
It looks racist to me, but I don't want to raise a flag if I'm not sure about the community guidelines... should this be flagged?
If you're referring to this answer, it's already been flagged by another user, so there's nothing you need to do. [Update: the answer has indeed been deleted, and the user suspended.]
In future, my advice would be that if you think something is racist, just go ahead and flag it. Racism is indeed against the Stack Exchange Code of Conduct, and will be dealt with by the moderators once it has been brought to their attention. Of course, different people have different definitions of what is and isn't racist, so flagging something doesn't guarantee its removal, but in this case, I'd say it's fairly cut-and-dry.
Although I don't know the full context of this statement, it appears to be a textbook example of bigotry and racism which goes contrary to the Stack Exchange Code of Conduct.
Politics Stack Exchange is a community for people from all nations and cultures. Therefore we do not tolerate it when nations or culture groups are described in such disparaging terms.
Please flag such statements.