no roaming charge to US? unlikely. Remember that they have to change money for something.. right :P? furthermore, those roaming fees also go to the US operator, so you cant just make them disappear. sorry to burst the bubble.
there is a roaming fee and also the charge for the call... that's double dipping!
Just make it cheap enough that I have no incentive to get a prepaid SIM from T-Mobile or AT&T. 25 cents/minute is acceptable, otherwise there are ways of getting it much cheaper via a voip forwarder and prepaid SIMs.
Yes, the carriers need to realize that consumers are NOT stupid and they can buy a temporary phone while traveling to the United States and avoid these ridiculous roaming charges.