Technically, the impediments to masking order enforcement enforcement are all sociopolitical or- as Umbran points out- fear of assault. AND all the liabilities that go with that.It baffles me when people claim you can't enforce masks. Umm, we enforce shoes and shirts. What's the difference?
There are a couple differences:
1) Shoes and shirts are already the norm. So, policing that is generally policing a very rare event, not a common one.
2) Folks get assaulted when they try to enforce mask use in the US.