I think this is key. It's also that companies enforce their policies. For instance, Visa and MC prohibit merchants from refusing to complete a transaction because the customer doesn't want to show ID with a properly signed card. There are some businesses who ignored this policy in the past but ended up dropping the ID requirement after a customer complained to Visa or MC. The same goes for minimum purchase requirements or imposing a credit card surcharge (where the law doesn't allow for such things).

I feel like there simply aren't the same protections overseas. There are a lot of merchants who don't seem to care about the policies of the payment networks, and this extends to DCC. You ask to be billed in local currency, and the response is, "Let's see what happens." (The merchant knows exactly what will happen.) Then the merchant gives you problems when you demand that the transaction be voided and run again without DCC.

I would say in the US that the cashiers would be a lot more willing to work with the customer in instances of DCC such that if any of us were to encounter it we would be able to opt out. There is a certain customer service oriented culture here that tends to do the right thing for the customer.

In the case of DCC at a restaurant in the US their motivation to help me would correlate with the size of tip that I would give.