If you're talking to an American, and they say "a can of tomato sauce," they likely mean this:I don't know either. Anyone?
In the U.S., "tomato sauce" refers to two distinct sauces. One is a tomato concentrate with salt and minimal herbs, used in cooking. This product is considered incomplete and not normally used as is. Related ingredients are tomato purée and tomato paste, each of which is similar but paste has a thicker consistency. Tomato purée and tomato paste have FDA standards of identity (since 1939) for percentage of tomato solids, and generally do not contain seasonings other than salt; tomato sauce is nonstandardized.[11]