How is blocking a product from entering your country imperialism? He’s shooting his own foot and thinks it’s a threat.
If sanctioning the countries that question the hegemony of the dollar does not seem imperialism to you...
Sanctioning a country is telling everybody not to do business with that country, monopolizing the market. He’s only saying that the USA won’t import from that country. The USA does not have a monopoly on consumption. His assumption that the other side will bend over is wrong. A voluntary exchange of money for products benefits both sides, and blocking it hurts the buyer as much as it hurts the seller.