{I'm no electrician, so this is all 'as I learned it'....}
A) In the US, the breaker is rated to protect the outlet:
20A outlet, 20A breaker, etc.
B) Each plug/jack set is unique; this stops you from accidently
putting 250 on the 125 power supply. But it also stops you from
using a 20A plug in a 30A receptacle...
C) Big exception: you can use 5-15R aka 15 amp receptacles
on 20A circuits. Further, the 5-20 receptacles accept either
5-15 or 5-20 plugs.