The USA is metric but the units have a wrapper over them to mask it from US citizens. Example NIST website https://www.nist.gov/pml/owm/si-units-length https:/

The USA is metric but the units have a wrapper over them to mask it from US citizens. Example NIST website https://www.nist.gov/pml/owm/si-units-length https://www.nist.gov/pml/owm/si-units-length >The value for the inch, derived from the value of the Yard effective July 1, 1959, is exactly equivalent to 25.4 mm.