Nikah is not right on phone because the condition of single meeting (ittihad majlis) is missing. It is possible by appointing agent, which can be performed in this way that the American lady appoints someone as her wakil (agent) in India to accept on her behalf the offer of nikah from the boy with whom her Nikah is fixed. So, if the wakil accepts this wikalat and he makes the offer of nikah or accepts the offer of nikah in the meeting of nikah in the presence of legal witnesses on behalf of the girl, then the nikah can take place.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband