In the U.S. milk comes in half gallon and gallon measures, which look like your 2L and 3L containers, respectively.

Sometimes you will find milk in waxed paper cartons, but that is not the norm. (It’s very common, however, for dairy products that are often bought by pint and quart — typically half and half, heavy cream, or coffee creamers.) Our fancier non-dairy creamers tend to be in tetrapaks, with less expensive (or at least distributed in higher volumes) creamers in plastic bottles.