Isn't your faith for the most part decided on where you live in the world?

To begin with it is decided by your parents and how they brought you up. Hopefully later it is your own mind that makes these decisions. It is true that where you were born can dictate the type of exposure you have to religion to some extent.

I think it can definitely have an effect, for example, if you live in a Latin country chances are you might be a Catholic and if you live in a Middle Eastern country, chances are you will be a Muslim. However, there are more factors that go into faith and religion, including how your parents raised you, life experiences and your own study of faith(s).

I would have said "for the most part decided by the culture in which you're raised." Part of becoming mature as a person involves critical examination of your belief systems and deciding which ones you want to keep, and which ones you want to throw away. I find it interesting in the extreme that most of those who go through this process come out the other side with similar beliefs about spirituality in general. ( No, I've not taken any surveys, just based on personal experience. )

No. It depends on how you are raised and your values. Geography is irrelevant.

To a great extent, yes. Many people born in the USA, for example, who embrace
the christian faith probably would have embraced Hindu if they would have born in
India, or Buddhism if born somewhere in Asia, or Islam if born in some Arab country.