> The problem with all of this is that the grid has to be transformed.

Yes, and that will be an enormous amount of effort, both to replace generation and to upgrade transmission.

At the same time, though, maintaining the existing grid is also an enormous amount of work. A large fraction of the power infrastructure will need to be upgraded or replaced by 2050 anyway, and the existing grid relies on enormous effort to extract hundreds of millions of tons of coal and gas every year.

"It will be a lot of effort" is true of anything to do with the overall grid, so it's not a useful argument against any particular proposal -- there is no easy option.

> To add in hundreds of millions of cars to the grid is going to break most of them.

“A future grid will absolutely be able to handle a future demand of transportation electrification.”

In fact, since EV charging has such flexible timing, it's a great option for easily integrating larger amounts of variable renewables such as wind and solar via time-of-use pricing (this article goes into more detail).

> I expect that many of the grids will require voltage changes. Going from 120 in the states to 220-240. Otherwise we will have to adapt millions of transformers for higher loads.

How would that help?

Changing home voltage from 120v to 240v is unlikely to do anything to help the grid, as the higher-voltage transmission lines would carry the same amount of energy (and current) either way. Running more transmission lines where needed is almost certainly a better option, and it's one the industry is already very familiar with deploying to address increased consumption.