Re: DCC in the US--I wouldn't be surprised if it became more common in areas that have large numbers of international tourists. There are a lot of places that aren't as well traveled, though, and for those DCC would be a pretty hard sell for merchants in the first place. After all, if you maybe only get one foreign card a week, are you really going to make enough from DCC to justify the effort (especially if you have to change your existing practices to make it easy for the customer to opt out)?

On that note, another factor that might make DCC less common is the cultural expectation in certain industries (e.g. restaurants) that the customer not run their own cards. Of course, DCC is still possible via the checkbox on the receipt method (like what Hong Kong apparently does/did), but I'm not sure it's worth the trouble for many to implement that approach.