Brits don’t mess around with tea I guess. I believe they’re mostly on 240v even for residential there. Correct me if I’m wrong but I don’t think it would even be possible to heat water that fast in the US on 120v.
[1] https://en.wikipedia.org/wiki/Mains_electricity_by_country#T...
You have 240 V at the panel, but you only run half for each common circuit.
Here in Singapore I think our pool pump uses three phase power, too. (Our plugs and outlets here in Singapore follow the British model.)
Continental Europe uses 16A radial circuits so the current rating is higher there.
EDIT: Of course, you can't run two kettles on one radial, but you can on one ring.
t = specific heat capacity of water * mass of water * degC deltaT / power
4.186 J/gC 1000g * 80C / 1800 J/s ~= 186 seconds