world power vs country

world power and country both are nouns.

Word	Noun	Adjective	Verb	Adverb
world power	Yes	No	No	No
country	Yes	No	No	No

As nouns, country is a hypernym of world power; that is, country is a word with a broader meaning than world power:

world power: a state powerful enough to influence events throughout the world
country: a politically organized body of people under a single government

Other hypernyms of world power include body politic, commonwealth, land, nation, res publica, state.

world power (noun)	country (noun)
a state powerful enough to influence events throughout the world	a politically organized body of people under a single government
	the people who live in a nation or country
	the territory occupied by a nation
	an area outside of cities and towns
	a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography)