The confusing part is (here in the states), all the kids do actually learn the Metric system in their grade school science classes, starting in elementary school (primary, I think they call it elsewhere). Everyone I know knows the Metric system, but they give me queer looks when I use it, e.g. in conversation. Not like it's insulting their American-ness or something either; I really don't get it. It's worst with temperature, where people have to fight their training to estimate the temperature in Fahrenheit.