other developed country. Since the 1960's the only period of increase in manufacturing employment was during the Clinton administration after NAFTA. They had declined steadily for 30 years before Clinton and for 10 years afterwards, just increasing again starting in 2011. To blame a 50-year decline on NAFTA seems to be searching for a boogeyman.
FDR actually proposed an International Trading Organization (ITO) in 1944 (along with the IMF and World Bank) but by the time negotiations were completed republicans controlled congress and would not ratify US participation in the ITO so it died. Who knows if the ITO would have become a reality if FDR had not died in office.
GATT was what created in the FDR/Truman era to promote multilateral control of trade. It was meant to be temporary until the ITO came into force but became permanent when the ITO was rejected by republicans. FDR did not want to see a return to the high tariffs and limited trade of the republican administrations that preceded him. Truman shared his commitment.
FDR created a strong economy and middle class not by going after foreigners and trading with them, but by going after our own 1%. He raised taxes on them, empowered unions, created and strengthened the safety net and regulated the way that banks and corporations did business. He did not blame other countries for our problems. In fact, he increased trade soon after taking office then set up the beginnings of the international trading system that exists today.