A lot of FM stations in the US have added digital broadcast capabilities alongside their FM broadcasts.
The Clarion head unit in my car has the ability to receive both FM and digital signals. However, it doesn't separate them very well so there is a lot more interference than with the non-digital Pioneer and JBL head units in my other vehicles. More improvement is definately needed.
I don't expect the U.S. to do away with FM until the majority of car radios on the road have digital reception capabilities. Of course, I could be wrong.
Mike