Might be better to calculate them separately for each locale and then tie-break with your own approach (min/max/avg/median/etc.)
Hopefully "es" will have Siesta support too.
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.