Reaction time

In the US, using a cord like this will either be harmless or create effectively a dead short. Typical breakers will catch the latter but it will take tenths of a second for a breaker to react in which time the electricity could kill someone.

Depending on circuit conditions a GFCI might intervene as well, they’re typically faster at reacting (needing a few milliseconds) but for a cable designed to handle full residential power, it’s still enough to kill a person in that small window of time