money transfers are in the top 5 sources for some countries Gross Domestic Product.
Most of the kids smuggled to the USA border have been returned by binational agreements. The El Salvador governent has a large socialist party which signed a peacce agreement in 1992 an later won control of the capital city and the country.
Check your sources.
What is this about other countries not getting visas? They are available to all, but there are the usual qualifications about having some kind of employment. That's a hurdle. But the main reason people aren't flooding in is because most people aren't trying to come here.