The best part about the breadth of NEMA standards is that the plugs generally match the power needed, so for light-duty appliances, which includes most household appliances that aren't permanently installed, if you were to accidentally touch a frayed cord, you'd be fine, because there's only 120 V on a 15 A breaker.

In some countries, it's common for every outlet in a house to have 240 V on a 32 A breaker, forcing four times as much power into any given resistive load, and giving an accidental touch of a frayed cord a much more dangerous outcome.

Perhaps also worth noting that while the US generally uses 277/480V for distribution (before stepping down to 120/240-208), Canada (also) uses 347/600V in many places: more power for the same copper cable thickness (or less copper for a given power, due to less amperage).

He created a 'periodic table' for plugs himself, though there's also a handy chart/illustration at:

* https://en.wikipedia.org/wiki/NEMA_connector#Nomenclature