I rely on the package markings for measuring tablespoons of butter.
For margarine, I have a nice slick metal scoop-shaped tablespoon. Easy to level, and can be cleaned out with a finger.
American recipes assume a standard 8 oz. cup. I could certainly see confusion and disasterous results stemming from using recipes from overseas which have different assumptions.
FWIW, my Pyrex measuring cup has a milliliter scale on one side, and I have a digital scale I could press into service for kitchen use.
