TR News just published our overview article comparing walking and cycling in Western Europe and the United States:
Buehler, R., Pucher, J. 2012. Trends in Walking and Cycling in Western Europe and the United States. TR News. Special Issue on Walking and Cycling 280: 34-42.
Note: TR News is copyrighted by the National Academy of Sciences. This pdf is posted with permission of the Transportation Research Board.
Here is a link to the article on the TRB website.