I encountered the after-work bar thing a couple weeks ago, on an out-of-town work trip. Really the first time in many years, since towards the end of my drinking days I didn't go to bars, I drank at home. Previous bar trips since I quit drinking, only a few of them, were large advertised events, but this was three of us and the other two people were drinking pretty quickly and putting on a buzz.
I noticed a couple things. One, I had no desire at all to drink, but two, I quickly felt out of place, particularly after the other folks started becoming obviously buzzed. Not quite superior, but I did start to get annoyed by the drunkenness, and found myself wanting to leave early (which I did) - not out of fear of drinking, but just because I felt like an outsider, a stranger in a strange annoying land.
These events do come up, and sometimes there is business value in tagging along because you get an opportunity to talk to colleagues (at least for a little while, before they get drunk!) in a social setting, so I'm glad I have no fear of them anymore. I would not have gone at all 4-5 years ago, but now it doesn't bother me except in annoyance and feeling like I have to go for business relationship reasons. Fortunately I'm only spending time there on/off over the summer, so it will only come up a few more times.