Most places either have soft water from their water supply, or people install a whole house water softener, if their water is hard enough to cause problems with mineralizing on dishes.
The salt for the whole house water softener would probably work, but the bags are pretty huge.
I am in the Bay Area. I bought some off Amazon no problem. It came from the US too.
> since we we generally don't have dishwashers with built in water softeners that need the salt.
Landlord installed a Bosch dishwasher, which has a water softener. The water is pretty hard (I can see by the shower faucet, and confirmed on the utility website). I'm assuming he didn't bother to import the dishwasher from Europe so it must be available in the US.
A quick check of Amazon.com [1] turned up a bunch of US-looking products, at least.
[1]: https://www.amazon.com/s?k=dishwasher+salt&crid=X6025PAVFBMS...
