Most of the people in the USA denying mask use are right wingers who choose to listen to politicians rather than scientists, that's the 90% problem, not what you're pointing out. Their leaders tell them masks don't work and they listen. Others listened to scientists and we're better for it but if half the country is ignoring it, it greatly reduces the effectiveness of masks. The CDC backtracked within a month or two that masks could be a good idea even homemade ones to limit the aerosols. To say anything else is nitpicking, we've have 6 months and people still deny it. Nothing you pointed out would have changed it since Trump double downed on not wearing a mask and his luddites followed behind him.