How does voltage affect boiling ability of a kettle? I was reading an article about the lack of electric kettles in the USA - the claim at the end states one reason is the lower voltage at the socket. Personally, I think that the main reason is that morning tea is not as big in the US as it is in the UK or Australia, but that's not the point.
Would a 120V kettle really take a "really, really long time" compared to a 240V one? Couldn't it just draw more current?
 A: In the US, your voltage is 110, and your maximum socket current is 15A (1650W)
In Europe voltage is 240 and the maximum socket current is 13A (fuse in plug) (3120W) The circuit could deliver 20A.
Dedicated circuits (for Cookers, Electric showers, and installed water boilers) can go up to 32A in europe, Not sure what the rating is in Europe, but I'd imagine it would be similar
Half the power, double the time (approx)!
A: The boiling time is a function of power, not voltage.  However, to get the same power at a lower voltage requires a proportionally higher current.  Yes, a 110 V kettle could draw more current to get to the same power as a 220 V kettle, but there are limits and downsides to drawing more current:
*

*The cord needs to be thicker.  More current means more copper crossection area.  That costs more, and makes the cable thicker and less flexible.

*Outlets have limited current.  The typical "standard" outlet in the US can provide 15 A.  20 A versions are available.  For high power appliances, like a electric range or clothes dryer, a special 220 V outlet is used.  These are large and klunky, and not something you find in a typical kitchen.  As a result, manufacturers don't make kettles with such plugs.

A: For a fixed voltage $V$ the power dissipated by the element in the kettle is $\frac{V^2}{R}$. To increase the power so that the water boils as fast in the USA as it does in the UK, you would need to reduce the resistance of the element. Alternatively, you just use the same kettle as in the UK and wait longer.
The domestic supply voltage in the USA is 110-120V AC, compared with 240V in the UK. The same kettle would take approximately $(\frac{240}{120})^2=4\times$ as long to boil in the USA.
The problem with reducing the resistance of the element is that it increases the current. To obtain the same power dissipation in the kettle at half the voltage the current must be doubled. This also increases heating in the wires supplying the electricity, which is less efficient and risks overheating the wires or - if the circuit is appropriately protected by a fuse - overloading the domestic circuit. Doubling the supply current increases power losses in the wires by a factor of 4, the same as in the kettle.
Americans use electricity domestically for their ovens as well as heating. These are connected to high-voltage circuits, which are more efficient - and quicker. I guess electrical coffee-machines are still run on 120V; perhaps Americans are not in such a hurry to get their morning coffee as the British are to get their morning tea. Stove-top kettles are far more common in the USA than plug-in kettles.
The low availability of electric kettles in the USA is a socio-economic question which I think cannot be answered by physics alone. Filtered or percolated coffee is very popular despite also (I presume) using the inefficient 110V supply, so I think this cannot be the main reason. Cultural preference for coffee rather than tea, and distaste for instant coffee, means there is little demand for electric kettles. Take-away coffee is extensively available and cheap in the USA, so there is less incentive to brew it at home.
