Asia.
Canada
I believe that the nation with the largest Christian population is China.
Brazil is not the largest; Brazil is the 5th largest nation in terms of population and area.
Russia is the largest nation in the world. It is in northern Europe and Asia
The population of Lagos, Nigeria is approximately 21,000,000. Lagos is the largest city in Nigeria. However, Abuja is this nation's capital.
China
The largest population country is Indonesia.
Indonesia is generally cited as having the largest Muslim population of any nation.
The African country with the largest population is Nigeria. It's population is expected to reach 155,000,000 this year.
Israel.
Indonesia