Why has outsourcing become a controversial practice in the united states?

Outsourcing has become a common business practice by companies and businesses in the United States. Outsourcing is a practice by which a business/company will hire an individual or another company (usually overseas) to perform tasks and objectives, for the purpose of reduced labor costs and more economic freedom. It is controversial because it takes away job opportunity from American workers and laborers, as well as deindustrialize regions in the Untied States that were once manufacturing giants (ex. Detroit and areas in the Midwest along the Rustbelt). It is also controversial because the job opportunity taken from American workers are moved overseas to developing regions where the worker's conditions are less adequate with longer hours and child labor being common practice.