Is that tongue-in-cheek? Of course they can boil a kettle.
It does take ages, though.
Conventional kettles seemed to take perhaps twice as long to boil in CA than in UK. Boiling water at 230V,13A in the UK is going to be much faster than 120V,15A in the US.
Assuming you're heating 300 mL of water. The specific heat capacity of water is 4.2 J / (g°C) [3]. If you're heating it from 20°C room temperature to 100°C boiling, that's a temperature increase of 80°C. The metric system is set up so that 1 mL of water weighs 1 g (give or take a little based on temperature, pressure, impurities, etc), i.e. the density of water is 1g / mL. Plugging in the numbers:
So approximately 100 kJ of energy is needed to boil 300 mL of water. One kW of power is a delivery of one kJ per second.
How much power do we have available? In the UK, there's 230V * 13A = 2990 W ~ 3 kW. In the US, there's 120V * 15A = 1800 W = 1.8 kW.
So in the UK it takes 100 kJ / 3 kW ~ 33 seconds. (One kW is 1 kJ / s.) In the US it takes 100 kJ / 1.8 kW ~ 56 seconds.
These times are likely lower bounds. Assuming the voltage and current given by the parent are correct (or you measure them directly and substitute those numbers) and you measure out exactly 300 mL of distilled water, the biggest source of error is probably the fact that you're heating more than the water. You also have to heat the resistor in your kettle or electric stove, the thermally conducting, electrically insulating housing for the resistor, the kettle itself, and the surrounding air. And water molecules heat unevenly (my thermodynamics is a bit sketchy but I think this is called a Boltzmann distribution [2]?) so a few will evaporate before the water reaches a uniform 100°C, carrying off energy.
My guess would be that the above effects matter less in the UK because the higher power means they would have less time to operate.
I'm pretty sure that this analysis deals correctly with the fact that the current is AC [1]; if any experts on the mysteries of power engineering want to correct me, please do reply.
It does take ages, though.
Conventional kettles seemed to take perhaps twice as long to boil in CA than in UK. Boiling water at 230V,13A in the UK is going to be much faster than 120V,15A in the US.