I have no idea about how the authorities in the USA act if they see you with earplugs or headphones.
And I agree that you can still hear your surroundings unless you rise the volume above reasonable. But it happens the same when you put a helmet on! Isn't?
But, for European drivers, I can tell you that here in Europe, if they see you driving your car, motorcycle, bicycle, scooter or anything with wheels on a road, with headphones you get a beautiful ticket... (200 €) and you’ll lose 3 points of your license.
It’s totally forbidden.
Same if you’re wearing a headset, despite it just goes in one ear…
And if you have an accident and you’re reported being wearing headphones or a headset, your insurance declines all responsibilities.
So if you drive in Europe, be aware of it, and be careful if you use headphones, earplugs or a headset…
Only the intercoms in a helmet are starting to escape (but not always) this prohibition, because, as I explained, they not IN your ears.
