After World War II was over, the USA assumed the lead in economic activity and economic expansion.

After World War II was over, the USA assumed the lead in economic activity and economic expansion. The abundant production of goods and services led American companies to search for foreign markets in order to sell what they could produce. Then, the world woke up to Supply Chain Management practices, and jobs started leaving the US to go abroad. Why did this happen? What change ? What are the consequences?