This isn't really correct though and gives a false sense of security. The house breakers are sized for the wires in the wall, not the device plugged in. Those should have their own internal fuses to protect themselves.

Most lamp cords are only sized 100ish Watts or ~ 1A with the bulb being the only fuse. If these somehow pulled 15A for any amount of time the wire would quickly get smoking hot but you still plug them into a 15A plug.

Devices are supposed to protect themselves. Most 15A devices will cause fires if they actually pull 15A for any amount of time. If you try to use a a small extension cord on your space heater, you will soon be smelling burnt plastic while never getting over 15A draw. That is part of why these are such a fire hazard.

Alos in the US a 20A socket is designed to allow a 15A plug to work in it, But not the opposite way as that would cause issues in the wall.