In what states is this not true? The National Minimum Drinking Age Act said that states needed to make the age 21 or else they would lose federal funding. Looks like they all complied from my quick research into it.
There is no minimum drinking age in Wisconsin if you are with a parent or guardian. Minors can order, possess, and consume alcohol legal at any age, under the discretion of the bartender, as long as they are at the alcohol establishment with their parents or a legal guardian.