Almost all car charging is done at night, when grid load is far lower. Charging will not be a problem, and there is no material shortage likely in the near future.
It is a cost cutting measure rather than an infrastructure limitation (people chose a 20A connection because of the standing charge cost) in the newer building, but I suspect that if a significant portion of the population need to double their contract and maxed it out during the night, there is going to be some work needed.
My guess is "they don't". A quick web search reveals less than 50% market penetration in homes of air conditioners.
That said I live in an apartment with 30A 100V service, and I've run 3 air conditioners at the same time no problem.
The poster mentioned Spain, which uses 230V (unlike the USA, which uses 120V), so 20A should be around 4600W if I did the calculation correctly. With a quick search I found a window AC with 18000 BTU using only 1700W, so even with 15A it would be possible to run one AC with plenty to spare.
And 4600 KW is only a couple tons. You'll need more than that for a 5-ton central HVAC to cool an average house in a hot or humid area.
I've certainly run into homes that couldn't add a clothes dryer circuit without major renovation involving the city.
Not saying it will be be an issue everywhere, but the span is too short for it not to be an issue in many places.
Given the short time frame, proof that there aren't issues would seem more prudent. Whether that's manufacturing capacity for batteries, or grid shortfalls in certain areas, or whatever.
Yes, it would require more rare earths than are currently economically feasible to mine if we replaced every fossil fuel engine with a permanent magnet electric motor of equal power.
The only real difference between the two is the design difficulty of the drive circuitry for the VFD to run the induction motor. That's largely a solved problem.