USA-style 100A service is at 240V, and larger appliances (including EV charging) use the 240V. So comparing a USA 100A service to a UK 100A main fuse is a like-for-like comparison.
However, although 100A (or even 80A in some areas) is the maximum single phase service here, the difference is that larger services are provided at three-phase - so the next step up in the UK would be 3x60A or 3x100A. Both of those sizes are available in homes in the UK, and you do find them at larger properties, particularly those built with electric heating.
These larger services are less common here, being a combination of smaller typical house sizes, much less common use of electric heating and extremely rare use of air conditioning, also that where you do get whole-house electric heating it's typically night storage heating.
However, a separate issue where I don't have figures for the USA is how the supplier's equipment behind those service sizes are shared. A street of 10 houses each with 100A service will never have a 1000A-rated transformer and service cables supplying them - the supplier will assume there is some averaging out of the load between the properties on the street, and will also allow limited overloading: it's OK to run a 100A-rated transformer at 150A for an hour or so while everybody cooks dinner, so long as there's time for it to cool down again afterwards. There's also a factor that under UK conditions maximum demand is in cold weather, so the service equipment can take more load without overheating since the outdoor temperature on those peak demand days is that much colder (the opposite applies in many parts of USA where maximum demand is for aircon).
In the UK, typical numbers are that each of these houses with 100A service (23kW max) is assumed to draw on average no more than 2 to 3kW depending on the size of house (so 8-13A long term average).
This is all fine for traditional domestic loads, but runs into trouble with both EV charging and solar.
There's no difficulty in installing 32A (7kW) EV charging at each house within the 100A maximum, but if everybody plugged in as soon as they got home (which is already peak load time for cooking the dinner, warming up the house etc.) then there would be a problem with the total load. Significant trouble is being pushed off for a little while into the future by time-based tariffs: notably "Economy 7" with cheaper rates starting at (typically) midnight, after most people are asleep and other loads are very low, but at slightly higher levels of EV adoption there would still be a problem with everybody starting their charging at midnight. It is in fact possible to support very high levels of EV adoption without major upgrades to the system, but only if the charging is spread across the whole of the night-time low-demand period (and possibly a bit at low demand times in the daytime too): if you assume all cars are EVs and they all drive the same mileage as they do now (and look at average numbers of cars per household etc), then there is in fact enough capacity to charge them all during the E7 period. So a mechanism to allow cars to charge at the right time to suit the local distribution system is going to be critical to enable high levels of EV adoption.
The same problem arises in reverse with solar: there's no problem connecting one 32A system on a house with a 100A supply, but if everybody in the street did it then at times of low load the distribution network wouldn't have the capacity to feed that much back into the grid. This time the problem favours California over typical UK conditions: with nobody using aircon and most people away from home in the daytime, peak solar generation coincides with minimal load on the local network and so all of it needs to be fed back into the grid.
