And in neither of these countries is there a huge level of non-adherence, at least in a transport setting. It seems allowing exemptions increases the incidence of people claiming them.
I agree that walking around such places you would think if they can get high levels of compliance (even outdoors), why can’t we. But that can be misleading since the people unable to wear masks may be stuck indoors, unable to participate in society.
Since you mention the USA, while compliance in commercial settings or air travel are high as you say, it’s not the same on other forms of public transport such as municipal buses. Everyone may bring a mask but they are not always worn properly. I have no view (or interest, in fact) on whether they are people against masks or people with exemptions trying to struggle through, but I’d estimate the numbers on public transport are comparable to the U.K. in any case.