That's not the current issue. Except for N95 respirators, basic medical masks and cloth masks seem to be readily available. K1052 is also wrong that legislation or EO solves the problem. It's not the legality of a public health order that's in question (see shelter in place orders), but whether citizens at this point would voluntarily comply and whether they would actively revolt.* Much of the country has somehow developed an anti-mask affliction; it isn't simply an extreme partisan issue. There is some general correlation with political beliefs, but at this point a mask-wearing mandate is only feasible in the most Blue-leaning locales and even then, you'll still have a lot of people who flout the rules.
* Remember OH Gov. Mike DeWine wanted to mandate masks to enter businesses, and he quickly realized it wasn't going to fly with citizens.
Americans collective anti-science fits a general pattern with Covid-19. Let's hastily reopen even if the metrics aren't quite there yet (no disaster yet, but the trendlines are scary), let's ignore social distancing and hygiene best practices, and let's unequivocally state now that there will be no lockdowns no matter what comes ahead.