> UK: 100 A x 230 V = 23,00 W
> US: 200 A x 120 V = 24,00 W
That's incorrect. The service drop in the US is 220V. It gets stepped down at the main load center to 120V for most of the regular circuits. So it's more like 48000W service in US houses.
Houses and apartments in Denmark have 3 phase service. My apartment's main breaker is labelled 40A @ 380V.
I believe the oven and hob make use of it, but I haven't looked myself.
I run an induction stove on 220V single phase every day here in the US.
240V. Since we're throwing around numbers, let's be accurate. This is a pet peeve of mine. We've been standardized at 240V since 1967, and it was higher than 220V years before that.
However, it seems like 220V was the standard before that [1], which is why it's still common parlance, referring to the "higher" voltage. Certainly I've heard many people in the trades still refer to it with the older term, even if the circuit is actually 240V.
So when you install a 400A panel in the US, it's 400A*240V which is 96,000W.
One thing I keep learning about the EU is ... do not generalize using Germany as the baseline. There are many areas where Germany is the odd one out, not the standard.
It's not about having 400 amps per se but about sizing the wire you put in the ground. Maybe you'll have a 200a main breaker and you'll only ever use 200 amps, etc. - but the hard part was digging and future you or other future yous will be happy that the wire was upsized when it was put in.
Same with conduit. Same with number of conduits.
I can't tell you how many times I have been very please with myself that I threw in that extra 3/4 conduit line when we dug that one trench that one time ...
UK: 100 A x 230 V = 23,00 W
US: 200 A x 120 V = 24,00 W
Edit: I am wrong in my understanding of US Voltages. It's 200 A per leg, which the US has two of.