fatherland vs mother country

fatherland and mother country both are nouns.

Word	Noun	Adjective	Verb	Adverb
fatherland	Yes	No	No	No
mother country	Yes	No	No	No

As nouns, fatherland and mother country are synonyms defined as:

Other synonyms of fatherland include country of origin, homeland, motherland, native land.

fatherland (noun)	mother country (noun)
the country where you were born	the country where you were born