I had a couple of days back in London recently and it struck me just how much lower alcohol British beer is compared to US beers. Obviously I am excluding mass produced 'light' beers like Miller Light from my observation, but when you stand up a decent local bitter from London, with its counterpart from a local brewery in Seattle (for example), you'll find quite a difference. London pints will be around the 4% mark whereas Seattle pints will be around 6%.
And the Brits, despite their reputation for big drinking, seem very happy to knock back a few pints without giving the ABV a second thought. Maybe that's why Americans have a reputation for drinking less than the Brits. That may be true in volume terms, but not so much when it comes to the alcohol levels.