Here in the
US, I have yet to see a piece of equipment with a cable or
plug with a neutral lead, that doesn't actually need it.
This is the other
confusing thing that I forgot: There seem to be a lot
of different plugs for three phase used in the US. In Europe we have
the red five prong "CEE" plugs (actually IEC 60309 / DIN EN 60309) for
I believe there is a 4 pin version of that connector. I am pretty sure I
have a couple somwhere. Earth and 3 phases (Delta), of course. It's still
red (incidating 415V or thereabouts). Whether it is commonly used is
another matter...
-tony