It isn't really twice as fast in Europe, though. While, yes, standard US outlets are 120V versus Europe's 230V, amperage also matters because what controls cooking time is wattage and wattage = voltage times amperage. In the US, kettles are typically 1500W or, if you dig a bit, 1800W. You can also find much smaller ones for things like camping and travelling, usually around 600-800W. Looking at European models (which is difficult to do from the US), I see that 3000W is pretty common in the UK, where they use ring mains: 240V at 32A, of which a maximum 12.5A draw is allowed per outlet. Mainland Europe, however, doesn't use ring mains, and commonly has circuits of 230V at 6A or 10A, although 16A are supposedly also common. Higher amperages also exist but for specific purposes only (same as in the US). At 6A, you can only do 1380W kettle, less than in the US, assuming intermittent use. If the manufacturer assumes continuous use, then it's limited to 1035W. For 10A circuits, it's a bit better at 2300W/1725W. Looking at what's actually available, I see a lot of 1200W and 2000W models, which aren't far off from what the US has. Only the UK has the higher 3000W models, as well as China, but China doesn't really count because their safety standards aren't really up to snuff.
Anyway, all of this is academic, because my 1800W kettle boils 1.5 L of water in about 3 minutes. That's good enough for anyone, and much faster than my gas stove is. If that minute and and a half was that important to me, I'd run a 240V outlet and buy a UK 3000W kettle, but it's just not worth it. What I'm saying is that the 230V versus 120V debate is missing the point. In the US, all circuits are 15A minimum, which is more wattage than the smallest EU circuits, and, in the US 20A circuits are practically standard for most purposes (you usually just have to have multiple outlets on the same circuit to use them, or the special 20A outlets or the 15A/20A combo outlets that I see in most new work around here. Yup, 20A devices use a different plug from 15A devices, but it's possible to have an outlet that can handle both at the same time.) This means that it doesn't really matter which voltage you use; you can do the same things with it.
Also, I'd like to point out that most US homes have split single phase 240V 200A service, while most EU homes have single phase 240V 63A service. Some older homes have 100A or 150A, but 200A is standard in the US for new homes and retrofits. And, in some areas, three phase is becoming more common. In particular, delta high leg three phase, which gives you 120V, 208V, and 240V circuits and 240V delta three phase power, which is the best of all worlds, again at 200A. The usual three phase is 120vY208v, which is nice, but you don't get a true 240V. This is also why we went with 240V over 230V like the EU or 220V like China. Most things will run just fine of either 208V or 240V, which means that we can use most of our stuff with either type of power. Only motors really give much of a crap, and they often have tapped windings so you can use either with the same motor. Anyway, 200A service is way better than 63A service. I've read that for new work, 125A service is becoming quite common in the EU, but I haven't seen anything about anything as high as 200A service for homes in the EU or UK. So, we got you beat there. Having everyone at 200A service makes electric car charging a much easier thing to do. Having three phase everywhere would be even better, but 63A 230V three phase, wattage wise is the equivalent of roughly 110A 230V single phase, so even if the euros are doing three phase, the US still has them beat. Now, 125A 230V three phase would beat out our single phase 240V 200A service but just barely. Of course, when the US eventually switches everyone over to three phase, it'll be at 200A, so we'll still win, especially if delta high leg gets used, which is what you'd want to use for retrofits from split single phase. USA USA USA!