That’s a contributing factor on the comparative desirability of an electric kettle here vs there, but I think the more significant part boils down to familiarity and need. Most Americans just don’t drink tea/cocoa/instant-coffee regularly enough want a separate appliance for it. And if the boiling is for cooking, most folk would just boil the water in the pot they will be cooking in, and probably with the lid off because we are lazy like that; time and energy efficiency be damned.