What has that to do with US signing the treaty? Shouldn't Kristof instead ask for Pakistan to enforce the treaty? Surely it would be more effective (if hypocritical) for the US to pressure other countries to enforce the treaty even without signing it. In fact, it seems that's what the US is already doing, at least in Afghanistan.
Perhaps Kristof believes the US would have more success in these international efforts if it were not perceived as hypocritical. But he does not make that argument. Instead, he uses heart-rending examples of battered or tortured women in Pakistan to make the direct claim that -- like Pakistan! -- the US must sign the treaty.