Speaking of contactless, apparently the significantly higher fees in New Zealand for it compared to EFTPOS (since it runs over Visa/MC) mean that a lot of places simply disable it altogether (
example). I wouldn't be surprised if merchants in the US start doing the same if/when it becomes more commonly used.
That said, the situation in the US is different in that merchants don't like any of the interchange rates as currently levied, so contactless use in and of itself might not be the last straw that those who are already unhappy will use to justify no longer accepting e.g. Visa.