Stubborn Refusal
Indeed, the EU had driven down mobile costs again and again by statue, high roaming call surcharges are almost gone, data is going the same way, and then the operators are voluntarily extending this scheme to other places they have presence, eg 3 in Australia.
I've no doubt it's better value for an American to buy a SIM from 3 in the UK and use it roaming in USA than use your own providers!