The USA uses metric all over the place. Everybody knows how big 2L is. Syringes are all marked in mL or cc. Socket wrenches come with 1/2, 9/16, 5/8 etc. but also 9, 10, 11. Athletes no longer run 100-yard dash. The "400" is 400m. Cars have 1.8L engines. People wear size 30 footwear, but also size 7.

Yes, the USA uses inches and pounds and gallons. They also use m, g, and L. And picas and fingers and miles and decibles and watts and joules. Mostly they don't know or care. If they do know and care, they are usually capable of using whichever unit gets the job done.