What are the requirements for a product to be labeled as "made in the USA"?
To be labeled "made in the USA" apparel and textile products must originate in the United States from "one step removed" in the supply chain. for apparel, this means the fabric in it must be manufactured in the United States as well. For fabric, the yarn in it must be manufactured in the United States in order to list it as the country of origin. According to FTC standards, footwear has to be "all or virtually all" made in the United States to claim it as the country of origin.
For more information on country of origin rules for apparel and footwear, see the Bureau of Consumer Protections page on labeling requirements
or their guide on the "made in the USA" standard