Things that make you go HMMM and thank a duck hunter.

Top 3 Largest National Christian Populations:

US - 246,780,000 (79.5% of the Population) 
Brazil - 175,770,000 (90.2% of the Population) 
Mexico - 107,780,000 (95% of the Population) 

http://christianity.about.com/od/denominations/p/christiantoday.htm