We might've been taught the metric system, but I think most Americans don't have the intuitive feel for the units in the way that we do for the English ones.
Though, it is a bit more complicated, at least for me. For example, if I'm weighing small objects/quantities, I definitely prefer grams and have a fairly good sense of how much of something there is if given a weight in grams. But larger weights, like people, etc., I use pounds. I know that a kilogram is 2.2 pounds, but if you give me a weight in kilos, I still have to convert it to pounds for it to be meaningful to me in a real world sense.
The same is true for something short in length. I understand intuitively what a millimeter is but start talking in meters for example measuring someones height and I have to do a conversion.
Though, it is a bit more complicated, at least for me. For example, if I'm weighing small objects/quantities, I definitely prefer grams and have a fairly good sense of how much of something there is if given a weight in grams. But larger weights, like people, etc., I use pounds. I know that a kilogram is 2.2 pounds, but if you give me a weight in kilos, I still have to convert it to pounds for it to be meaningful to me in a real world sense.
YMMV, though.