To show the flag means to stand up for support or defend someone or something, which is what the speaker is doing by showing the flag for their country.
Consider the statement "Whenever I go traveling, I make it a point to defend and support my country by showing the flag for it when it is being insulted or made fun of. ". Is the statement "My country is often a target for insults or gibes abroad, so whenever I go traveling I make a point of showing the flag for it." false? Yes/no/unknown