The recent Pew study on Global Christianity (see next post) has this breakdown of Protestant denominations worldwide:
Raise your hand if you believe the following statements are true.
1) In 1970, Christianity was a predominantly Western movement, but by 2000, surging growth in Africa, Asia, and Latin America meant that the majority of Christians lived outside the West.
2) While Christianity in the United States was declining notably in the 1990s in numerical terms, in African countries like Ghana it was growing rapidly to majority status.
3) The number of career missionaries from the West is declining as the church of the “Global South” takes up the mantle of leadership in mission.
For the answers to these questions and some discussion on America and shifts in “Global Christianity”, see World Christianity and the American Churches by Andy Crouch (Books and Culture)