Clerks do get charged in the U.S. fairly regularly, depending on the state. In many states, it's a strict-liability offense to sell alcohol to a minor, without the prosecutor having to prove intent. Usually the clerk is exempted from liability if the minor showed a fake ID (that wasn't so bad as to be obviously fake), or if the minor looked clearly over 26 or 30, or whatever the state's threshhold must-ask-for-ID age is. If it's a 20-year-old who didn't clearly look 30+, though, and you didn't ask for ID, it's a criminal offense (in some states).
In some states the clerk is required to check ID on everyone, even 70 year old guys with canes. It's ridiculous, but the intent was to remove the element of judgment entirely.
