Well I'd argue the minimum proportional response to achieve the ends (i.e. there's some carrot/stick combinations that would not be 'right', or worth the international outcry... and even in that window why go for overkill?)

The problem is that I don't think the U.S. has a lot of carrots at any given time (what are we going to do, lodge a formal protest?), and you'd certainly not want to start off with the stick.