I don't know if anyone else assigns second nationalities to players to fill out international teams, but I waste WAY too much time doing so. I just discovered an old-fashioned free internet site where you can enter a name and it guesses the origin. Great for the Eastern European names in particular, although of course YMMV (I don't think Josh Jung is Korean, for example

).
Anyway, use it in good health:
https://nameoriginfinder.com/?