How do you know if a country is masculine or feminine?

Answer 1

No choice but to actually learn them individually. There is not quick, easy or simple trick/rule to follow. Don't feel daunted though, even the French often get them wrong.

Answer 2

In linguistics, countries are assigned a grammatical gender based on language conventions rather than any inherent characteristic of the country itself. Typically, masculine and feminine genders are arbitrarily assigned to countries by linguistic tradition in certain languages.