God bless America
I've found this little singer on YouTube and I noted she said "her" referred to America.
I would like to know whether the feminine gender is only used for one's own country in English, with a meaning of affection, or it's a general rule.

Just to make an example, is it correct for a French citizen, while speaking English, to say "her" referring to, for instance, Spain, or should they say "it"?

You should keep watching the video till the end (it just lasts 1 min. and 50), the way that little honey thanks the public is very funny!

https://www.youtube.com/watch?v=94JQS6itgYI

Question

God bless America
I've found this little singer on YouTube and I noted she said "her" referred to America.
I would like to know whether the feminine gender is only used for one's own country in English, with a meaning of affection, or it's a general rule.

Just to make an example, is it correct for a French citizen, while speaking English, to say "her" referring to, for instance, Spain, or should they say "it"?

You should keep watching the video till the end (it just lasts 1 min. and 50), the way that little honey thanks the public is very funny!

https://www.youtube.com/watch?v=94JQS6itgYI

Answer

Neither. There is no reason to do it, it's purely a stylistic choice in the lyrics of the song. It's by no means a grammatical rule. As you said, it's a way of showing affection through personification. Myself, I would never use a personal pronoun to describe a country and I think that would apply to the overwhelming majority of native speakers.

Answer

It is used affectionately to one's own country.  "She" or "her" can also be used in the same manner for a car or a boat or any other object that you have affection for and are attached to.  This gives the object a sense of personality.  In the same way, sometimes people name their cars, etc..

Answer

When we do use it, we usually refer to our parent countries using a feminine pronoun such as "she" or "her." In case of other countries we just use IT. Unless it's like a very formal social documentary or a history lesson about the world, where it's fine to use "she" or "her" for other countries as well.