I don't know if it is just because I grew up in a pretty sheltered life when it came to alcohol or if all of Europe has drastically different views on alcohol then the U.S. but it is one of the things I have noticed since being here.
Pubs really are part of the culture here. Pubs are classified by what breweries they sell their beer from. (Similar to fast food chains selling Coke or Pepsi) The cheap pub chains like Witherspoons are seen similar to Walmart as in they destroy local businesses through price. Another thing that is apparently killing pubs is cheap liquor from grocery stores.
In the U.S. I would say that you have a problem as soon as alcohol affects your life. Here alcohol is a problem when it is depended on. They are genuinely surprised when I say that if you were to show up for work with a hang-over multiple times a week people would start to worry. Here the sign of a good home-town pub is the pub owner has keys to the regulars houses to get them home when they are to drunk.
Level of drinking
I know I'm with a lot of students so there is heavier drinking but at pubs stag or hen parties come in all the time and are quite annoying because their goal is to get as drunk as possible. As I previously talked about getting drunk and ending up in some anonymous bed is seen as OK. It is seen as something that happens to everyone that drinks and it is up to the friends to take make sure the drunkest person doesn't end up with a psycho.
Drinking in public
Now I am aware this has to do with the public transport system here. Most of the places I have lived in the U.S. you had to drive home so you didn't see people staggering down the street. Well at least non-students. I still remember "drunk alley" in Oregon. I just get caught off guard seeing people in their 50's and 60's red eyed and listing as they walk around on a Friday or Saturday night.