What other supermarkets as Walmart require wearing a mask from 20th july in the US considering the further risks of Covid-19?

Wearing a mask while shopping in Walmart is a must starting from 20th july. In what other shops do we have to cover our mouth and nose? Does it have to be a proper mask or a scarf would do the job? I've read how this preventive campaigne was done in the EU and there people were allowed to wear a scarf, too.