It is not designed to help build the economies of the underdeveloped and developing nations. The nature of capitalism is to keep neighboring countries in a state of subservience. In this day and age it means subservience to U.S. monopoly corporations. The southern hemisphere countries are up to their necks in debt to the U.S. banks. In fact what is agreed to is acceptance of austerity programs that do the opposite.
Poverty increases tenfold, forcing workers to migrate in search of living-wage jobs.
Thus, immigrants keep coming by the thousands. Nothing is going to stop them as long as their home country remains poor. The customary contradictions of capitalism are present here also. Big farms and other businesses, such as the garment or hotel industry, demand low-wage workers. Government officials, on the other hand, are using the issue to get elected.