There are many reasons to support universal standards for countries participating in free-trade agreements. Many of today's most pressing problems such as climate change, resource exploitation, human rights abuses, economic disparity, and overpopulation stem from an uneven playing field throughout the world.
Require that all countries who trade with the U.S. meet certain standards protecting the environment and its people. We should only trade with countries who protect their people and their environment.
In many cases, the U.S. would benefit by helping other countries reach acceptable levels. We should consider helping countries be sustainable, and only help those who help their people. Everyone would benefit.