When you fill out your Application for Naturalization, Form N-400, you will need to mention your country of birth and country of citizenship in Part 2. Sometimes these two countries are different because of how you acquired citizenship in the first place.
To give you an example, let’s assume you were born in Canada, and your parents were immigrants from another country such as Spain. You will need to specify Canada as both country of birth and country of citizenship on Form N-400, because Canada acknowledges the right of soil. Put simply, a child born on Canadian territory is a Canadian citizen no matter the nationality of the child’s parents. Your country of citizenship can also be the country where you naturalized.
Otherwise, if you were born in Spain by Canadians, your country of birth will be Spain, but your country of nationality will be Canada. Thus, you will need to mention different countries on your application form.
Lastly, if you lost your citizenship through renunciation, you need to write the last country where you were a citizen.
Write the name of the country of birth into the field 10 in Part 2, even if the name of the country was changed since your birth. Note that if you are a dual national – a citizen of two countries at the same time – you need to write into the field 11, Country of Citizenship or Nationality, the name of the country that last issued your passport.