The US was an original signatory of the Meter Convention. Our customary units have been based on metric units since 1893. Our food packaging features metric units. Our scientists use metric units. Our school children learn the metric system. Our military uses the metric system. Our cars are built with metric fasteners.
Changing informal habits takes decades and has questionable benefit. Canada tried it in the 70s and is going to take another generation at least to fully convert for informal use.