What "whiteness" means to me

Having grown up in idle suburbia my whole life, my view of whiteness has become rather cynical. To me, whiteness means being able to pass off as part of a majority. The term "White" has a connotation of being "unhip", "WASPy," etc. What confuses me is why some groups are excluded and why others are assimilated.
Technically, the term "Caucasian" also includes Arabs, Indians and Ashkenazi Jews. But almost none of these groups are considered "white enough," even though they have a similar ethnic background. For example, even though Governor Piyush "Bobby" Jindal is Caucasian, he is not "white," even though he fits in the same, commonly-used racial category. Also, no sensible person would make anti-Irish caricatures, but how many people would bat an eyelash at a caricatured suicide bomber.

My dad having mainly Sicilian ancestry, as a kid I had joked that he was really "black" due to his slightly darker skin tone. This may sound like inane, childish comments, but some "pro-white" groups exclude Italian-Americans primarily for that reason.

The "Whiteness and American Film" article mentions how many audiences considered the comic book and film antihero Spawn a black superhero, while not making any racial analysis of characters like Batman. In my mind, filmmakers automatically assume that middle-class, well-off white people are the target audience. Apparently, a film with a black protagonist will not be successful if producers primarily emphasize his race and cause controversy because of it. (From what I've read, Spawn's racial background have not been emphasized as often as his supernatural powers.)