We have benefited through most of the 20th century from trade. It has helped to raise American standards of living, it has helped to create jobs. And I agree with Paul Samuelson, the very famous economist, who has recently spoken and written about how comparative advantage as it is classically understood may not be descriptive of the 21st century economy in which we find ourselves.Mankiw notes that Clinton looks to be referring to Samuelson's paper in the Journal of Economic Perspectives. Mankiw then continues to point out some of the problems with many of the (mis)interpretations of the Samuelson's paper and to make the point that comparative advantage is far from obsolete.
Clive Crook offers this critique, while the view of the Adam Smith Institute is here.