It takes longer but not by much. It’s the volts times amps that indicates the actual work done.

Having lived in the UK and the US. Kettles only take a min or so longer in the US. They tend to be 1.6kw rather the. 2kw. Your plugs are slightly higher current then ours. Although your plugs always worried me as rather small connection surface wise.

But people in the US just do not consider boiling water as often as we do. Coffee and green tea tend to be ruined with boiled water.

Whereas many Brits very much prefer the taste of black tea when the water is boiled. It has a significant effect of the flavours released.

As such. Even before electricity was common. Most houses had a kettle that could be boiled on gas or the open fireplace. It’s been common in UK houses since the late 1800s.