US I think it's more a consequence of looser drink driving laws. Larger distances that do make just getting to the pub a bit more of a challenge, and just the massive car culture in general congeals to a looser cultural attitude towards it I suppose. Though I'd say drunk drivers are looked down upon in the US by most everyone and a DUI conviction has some really serious implications beyond the legal penalties since employers look at it as basically "this person is a dumbass that can't fucking plan ahead"

The thing is though we can't really talk about the differences in US vs UK culture around drunk driving I think before we talk about the differences in drinking culture in general. Laws on alcohol consumption in the US are generally a lot stricter, attitudes towards drinking in general tend to be a lot more harsh with the judgemental teatotaler types everywhere.

The cheeky lunch beer I've had with UK work colleagues would probably get your fired in a lot of places in the US at the worst. And I've had Americans call me an alcoholic to my face because they saw me have a single beer with dinner two nights in a row.