The Country of Origin* (COO) marking has been required for all goods imported into the U.S. since c. 1906. It is still required on all imported products today, except for firearms. The GCA '68 changed the requirement for firearms to show the importer and the caliber, but not the country of origin.
Either marking can be applied in the exporting country or in bond in the U.S.; usually for non-firearms, the COO will be applied in the exporting country. For firearms, it is often applied here before official importation.
*For youngsters, note that at one time the US actually made products and traded with a number of countries; under the current administration, US manufacture is forbidden, and all imports come from China, so the COO might not be necessary.