And we need groups of locales for teams that are split across multiple locations; e.g.:

  new_date = add_workdays(
    workdays=1.5,
    start=datetime.now(),
    regions=["es", "mx", "nl", "us"],
  )

Hopefully "es" will have Siesta support too.

Might be better to calculate them separately for each locale and then tie-break with your own approach (min/max/avg/median/etc.)

Don't forget about regional holidays, which might follow arbitrary borders that don't match any of the official subdivisions of the country. Or may even depend on the chosen faith of the worker

Pulaski day in Illinois. Or Reds Opening Day in Cincinnati.