I said "an employee group of people interested in Swedish culture". I did not say "Swedish-only group". I think that difference is the nub of this topic.
If a non-Swede were to show up to the Swedish group, and be harassed (eg, be told to leave on the basis of not being a Swede), then that's an civil rights violation already in the US.
Was tejohnso's question specifically about employee groups which discriminate membership on the basis of national origin, sex, etc.?
As I understand US law, an employee organization which uses donated company space or funds and which discriminates on the basis of sex, national origin, veteran status, etc. is covered under the same anti-discrimination laws that the company itself is.
More specifically, "It is illegal to harass an employee because of race, color, religion, sex (including gender identity, sexual orientation, and pregnancy), national origin, age (40 or older), disability or genetic information." ... "The harasser can be the victim's supervisor, a supervisor in another area, a co-worker, or someone who is not an employee of the employer, such as a client or customer." (quotes from https://www.eeoc.gov//laws/practices/ ).
Since tejohnso was talking about things which were at US tech companies, I assumed that tejohnso was referring to currently-legal US practices.
Is "Black Employees @ Netflix group" restricted to only people who self-identify as black? Or is it also open to people who do not consider themselves black? (Eg, National Association for the Advancement of Colored People (NAACP) membership is not limited to colored people). I do not know. Nor do I know if it uses Netflix resources.
I do know that my sister's women's group at a large international company has men who are members.
I think your statement "The test of membership is 'personal interest' which is not an inherent, immutable trait" is too narrow. Religion faith is a mutable trait. Just like we both would reject an on-site employee club which excluded non-Swedes, I would also reject an on-site employee club which exclude non-Protestants.