You also have to consider how the removal of De Minimus could backfire against him, personally. Say he stops making enough money on his red hats using materials solely in the United States. (Fat chance most of the production is done here, but I don't feel like tracing the web of his supplies, so we will give him some benefit of the doubt, as most of the production of his merch is handled by, I'm assuming, more competent people within his empire.) Say the Chinese sweatshops are a more prudent business decision as a source of manufacturing. The removal of the De Minimus clause could be the reason a red hat sits in a supporters cart instead of being purchased.