[xoa]

>Alternatively, many of the private space companies don't have citizenship requirements.

In America at least private companies are equally covered by ITAR, so they do have citizenship/greencard requirements (or need a variance that is nearly never granted in practice). SpaceX can't just hire international talent as it wishes. I assume there may be similar rules in some other countries, though certainly not all. But it's not merely a matter of private vs public fwiw.