Good point about the Europlug/Schuko etc. I believe that the smallest flex size specified in most of Europe is 0.75 sq. mm, whereas in the U.K. we also have 0.5 used on some small devices (or a near equivalent in pre-metric days). This has certainly gone on for many years, and I don;t like to think about how many old table-lamps were wired to BS546 plugs on 15A circuits with such thin wire.

Andy,
The NEC in the U.S. allows 15A receptacles to be fed from either a 15 or a 20A branch circuit.