The geographical location.This determines its flora,fauna,geographica formations,weather,resources etc.. and that is what contributes in shaping people's life styles and culture primarily.

the way people in each country organize themselves, agree or disagree to a common hierarchy of important stuff and beliefs towards a better future, the existence or lack of common moral values kept to define good citizens, the tolerance towards who have different opinions the language and history, the quality of the educational system.

Imaginary lines called "borders" ;)

gumustaka! not religions , politics, gevernments, ...........etc etc for sure. but simply —————— love —————— can change and unites the whole world. as we say it in tagalog —————— ma hal ki-ta ——————

All of those 3 things