Whilst on the subject of Amps, don't forget that US domestic supplies run on half the voltage that UK ones do, so require twice the current to deliver the same amount of power. Direct comparison of numbers doesn't work.
I was talking to a neighbour over the Bank Holiday weekend who had just come back from a month in Germany working with a colleague who owns a Tesla S. The trick apparently isn't to charge the battery overnight but to keep it topped up by "sipping" through the day when stopping for lunch or a cup of coffee. With the Tesla "supercharger" that's very effective for someone doing a lot of mileage on relatively short trips, especially as the charging is free for the life of the car. You do, of course, need the infrastructure to do so.
Andy