In use for some things, yes and you can do conversions from the US version of Imperial to SI and vice versa.SI has been an American standard for more than twenty years.
http://physics.nist.gov/cuu/pdf/sp811.pdf
But SI units are not the same as customary US units in common use.
Those with a big appetite might order a 16oz steak but you are not very likely to be offered a 450 gram choice.
A very tall chap might be 6ft 8in but he wouldn't usually be described as being over 2 metres tall.
You buy your milk by the pint, quart, or gallon.