To find the transmitter details for a broadcast station in the USA, use this URL
http://transition.fcc.gov/fcc-bin/fmq?call=WTMP (replace WTMP with your station letters), or replace 'fmq' with 'amq' for an AM station.
Some differences between US and UK broadcasters:
Anything below 10KW ERP is a small station
FM channels are always spaced 200KHz, e.g. 88.1, 88.3, 107.7, 107.9 so there is no real overlap between adjacent channels. Stations in the same city are usually spaced 800 KHz.
AM channels are 10KHz spaced, and the band goes up to 1700KHz