Is Ethnocentrically a Word?

the belief in the superiority of one's own group or culture. Also ethnocentricity. — ethnocentric, adj. -Ologies & -Isms.

What is it called when a country thinks they are the best?

Nationalism is the belief that your country is superior, without question or doubt.

What is it called when you judge another culture?

Such attitudes are an example of ethnocentrism, or evaluating and judging another culture based on how it compares to one's own cultural norms. Ethnocentrism, as sociologist William Graham Sumner (1906) described the term, involves a belief or attitude that one's own culture is better than all others.