Both, given the conversation on twitter with Gad Saad. What I get out of that is that it's reasonable that nations tend to accept immigrants who are more like them, because that comports with human nature. That's not to say that we would want to exclude people just because they come from places which have very different values, but that we would want to seek out people, regardless of where they come from, who can assimilate into a society with our values.
So Western values: liberty, freedom of speech, religion, thought, association, etcetera.
And I woudn't say that culture is the problem. Diverse cultures can easily coexist peacefully as long as the general societal and individual values aren't too diverse. A culture which values pedophilia will only work in Hollywood, with any long term acceptance, for example. It's not going to play well in middle America. So, the people who are most accepting of the Western values will likely do well in Western societies, regardless of their cultures.
