US vehicles are equipped with the BM53 radio which doesn't support TMC. The BM54 radio will work in the USA but you will run into difficulties with the frequency band as trapdoor mentions along with the step increments on the FM and MW/AM bands.

Also, if you have Sirius Radio, the BM54 will not recognise the Sirius Tuner ....

BMW are introducing a new system in the USA, called RTTI (Real Time Traffic Information) on most of the new MOST vehicles in 2007 with Navigation/I-Drive. It will function very similar to the TMC and Vi+ systems in Europe with dynamic re-routing capabilities. No news yet if this system will be available on I-Bus cars, but given that the new X5 is moving over to MOST, and the current 3, 5, 6 and 7 are all MOST ... this really only leaves the Z and X3 in the model range using I-BUS, so its very doubtful ..... but you never know !