How are members of white ethnic groups such as Italian Americans and Irish Americans able to express situational ethnicity while members of non-white racial groups cannot?

Answer 1

General Argument
The argument is that situation ethnicity is an ethnic identity can be either displayed by using clothing or other accoutrements or concealed by the same mechanisms at the whim of the person. In this case, the idea is that Italians and Irish can "play up" their distinctiveness in White-majority crowds to look unique, but can pass as White in other situations which results in them receiving "White-privileged" treatment. Non-White persons cannot pass as White, meaning that they cannot receive "White-privilege", and therefore, have no situational ethnicity, because they are consistently Non-White.

Criticism
Of course, this argument is nonsense. Every ethnic group can engage in situational ethnicity, regardless of whether these ethnicities are racially White or not and there is no serious thing as "White-privilege". As for other groups having situational ethnicity, this can easily be displayed. Among Hispanics, a Puerto Rican will take on more "Puerto-Rican" aspects and behaviors to have a unique ethnicity, but in the wider society will blend into the Hispanic Crowd. Blacks in the US who want to excel academically change their behaviors between academic settings and social settings in order to more effectively take on the different "ethnic characters" of a studious person and a more ethnic African-American. Every person has aspects of their character or identity that they promote to different degrees in different contexts. It is not a uniquely White phenomenon.

To the second point, it is incorrect to see privilege as a construct based on race rather than seeing privilege as a result of (1) wealth, (2) social prestige, (3) education, (4) hard work and perseverance, (5) personal connections, (6) attractiveness (both physical and behavioral), (7) personal values, and/or (8) interpersonal skills. These actual privileges do result in different behaviors from third-parties and not discriminate based on race. A Black Man in a freshly pressed business suit is going to be treated far better than a White Man in torn-up and ratty clothes. The Black Man in the Business Suit is passing as a sophisticated and educated person, which is why he is well-treated.