Learn English – Word for “being overly protective of petty things”

In your example, I would probably use the word smartass or a more milder smartypants.

I think condescending, a word you used later in your question, conveys perfectly well what you're trying to ask.

Does that email make me sound too condescending?

For terms that see this in terms of a nation:

nationalistic

relating to or showing a belief that your country is better and more important than other countries (from Merriam-Webster)

jingoism

the feelings and beliefs of people who think that their country is always right and who are in favor of aggressive acts against other countries (ibid)

See also fascist.

for terms that focus on the racial aspect, I might say ethnocentric

having or based on the idea that your own group or culture is better or more important than others (M-W)

or tribal thinking.

A good pejorative adjective for expressing this sort of biased thinking is "jaundiced"