(I got a electric tea kettle with a built in thermometer not too long ago, so this is an interesting issue for me.)
In the UK (& Ireland) "tea" means black tea. You can get fancy teas, but "tea" on it's own just means black tea.
We put milk in it aswell.
With it's own ISO standard http://en.wikipedia.org/wiki/ISO_3103
(An acquitance of mine has a kettle like yours at 1000m elevation, and with the thermostat set to 100°C it does not stop boiling of its own accord).
"Similar to every British tank since the Centurion, and most other British AFVs, Challenger 2 contains a boiling vessel (BV)[citation needed] also known as a kettle or bivvie for water which can be used to brew tea, produce other hot beverages and heat boil-in-the-bag meals contained in ration packs.[9] This BV requirement is general for armoured vehicles of the British Armed Forces, and is unique to the armed forces of the UK."
[1] http://en.wikipedia.org/wiki/Challenger_2#Crew_and_accommoda...
When renting a house for a holiday in USA once, my family went out to buy an electric kettle to make tea & coffee, and they weren't as common in shops as we thought. That was a weird eye-opener.
I've travelled a fair bit and I've never, ever seen as many kettles as in Britain.
The US/UK difference is mostly due to the electric supply I think. At 230v with a max draw of 13Amps per socket UK electric kettles boil fast compared to US ones in my experience.
Electric kettles are common here even though we use 110V power. I've never timed it, but I think they can bring cold water to a boil in maybe 3 minutes, which is okay with me.
If electric kettles are rare in the States then I think it's because of a cultural difference, not because of the mains voltage. Sure it would be convenient if kettles boiled faster, but I don't think it makes that much of a difference.
I did grow up with one though. My parents had previously lived in a house with a very small kitchen with no convenient place for an electric kettle. When they moved they kept their stove-top kettle until it burned through (about 10 years) and replaced it with an electric. I bought a stove-top kettle a few years ago for the same reason. It still comes out occasionally when an electric kettle breaks (which is quite often if you live in one of the "hard water" areas of Southern England.)
The trick is to every now and then turn the kettle on with no water in it. The calcium on the spiral at the bottom of the kettle will break into big chunks and fall off, if you just turn the kettle up side down they will fall out and you'll have a heating element as good as new (don't let it get too hot obviously, as that will damage the heating element and/or kettle itself).
I'm speaking as an American myself: I have a very hard time, despite being conscious of it, not thinking of all things American as a baseline for normalcy. I know, intellectually, that American dialects stagnated for centuries after being imported from Britain and eviscerated by Webster, but I still think of "colour" as a foreign and exotic spelling.
I suspect one of the reasons for the popularity of small electrical appliances in Britain is that electricity is traditionally cheaper than gas, which is the opposite of what you'll find on mainland Europe.
Rubbish, electricity is around 3x more expensive per KWh than gas in the UK. The UK has traditionally been a big gas exporter, too.
Electric kettles are used for convenience (faster, turns itself off) rather than financial reasons. Most people have little clue about what contributes what to their energy bills, too.
Presumably they are slower in the US because of lower mains voltage (x Amperage).