Quote Originally Posted by Rob View Post
US: I could care less.
UK: I couldn't care less.

I think the UK version is gramatically more correct for the implied meaning.
You are correct, except (oh dear, I'm indulging in pedantry) it's not grammar, I guess it must be syntax.

The cited US usage only seems to have evolved in the last 35 years or so. I always want to ask, "How much less could you care? "