Offtopic question: just curious, are American students now learning at school/university inches or cm? miles or Km? Celsius or Farenheit?
For the last past half century or more in the USA, metric units have been extensively used in science and medicine and they are now creeping into everyday life. In photography, we measure the focal length of our lenses in millimeters and resolution in lp/mm, but photographic paper is still measured in inches. Our wine comes in 750 ml bottles, but beer is usually sold in 12 ounce containers. Mechanics have to have a set of metric wrenches, since metric nuts and bolts are widely used in American machinery and universally so with imports. Wikipedia
has an informative article on metrication in the United States, and the article mentions the failure of a NASA Mars orbiter because one contractor used English units while others used metric units, and someone forgot to convert between pound force seconds instead of newton seconds.
To answer your question, the metric system is taught in our schools, but those who do not use metric units forget much of what was taught. One reason that the metric system has not caught on in the USA is that Americans tend to be traditional and do not like to be told what to do by the government.
Not mentioned in this thread is that the metric system has been superseded by the SI (Système International) nomenclature. American physicians have been measuring blood glucose concentration in milligrams per deciliter for decades, but now some journals are reporting it in the SI units of millimoles per liter. Under SI, if we photographers were still doing chemical photography, we would have to go to the camera store and tell the sales clerk to give us 1 mole of sodium thiosulfate!