For what it's worth, the U.S. has adopted the metric system, only not exclusively. You'll find metric measurements on almost everything in the supermarket, in addition to the old English system.

Speaking of the old English system... Did you know that the English changed parts of their system after we adopted it? They no longer use the same system of liquid measure that we still use. U.S. gallons, quarts, pints, and even ounces, are entirely different than U.K. (Imperial) measures of the exact same names. For example, a U.S. pint is 16 ounces, totaling about 473 ml., whereas a U.K. pint is 20 somewhat smaller ounces that add up to about 568 ml. This actually boggled me (and sidetracked me into learning about the different systems) when I was reading some futuristic/dystopian English novel that complained that the new half-liter glasses were smaller than the old pints the protagonist was used to. After all, as an American, a half liter would be an improvement on our pint glasses!

And don't get me started on pounds. Between Troy, Avoirdupois, Tower, Merchant and London pounds, it's easy to see why the English embraced the kilogram. At least we mostly only have two of those to deal with, unless you're a coin collector trying to figure out what an old silver coin is equivalent to.

So, metric weights and measures are an officially-adopted system for commerce in the U.S., and it is a regulation that you'll find them on most packaged foods and beverages. But, except for hard liquor, you'll also find the old measures.