I know you can't use televicion shows as a real measure, but they most certainly can have an influence. As such I always have found it strange, that you often hear characters decribing themselves as Irish-American, Italian-American, African-American etc etc. I don't think a script-writer has ever penned a line for a character to be described as English-American, Dutch or German/French American either.
It's a curious thing, that some ethnic or ancestral groups cling to their former identity and insist on hyphenating themselves, while others fully assimilate and take pride in identifying themselves as Americans.
I am of Irish/English and French-Canadian extraction, yet I consider myself to be solely an American, period dot. Yet when I was in school, I found myself surrounded by people who were fanatical about their Irish heritage, with some going so far as to actively support the IRA. I went to an upper-crust Catholic high school, so minorities were present but weren't as militant and separationist (if you excuse the coining of that word) as they were elsewhere.
Generally though, I'd say that in the USA, groups that were at one time the object of persecution or discrimination are more likely to cling to their historical identities--the Irish really had a bad time of it 200 years ago, and of course everybody knows how the black Africans suffered. More recently the various tribes from south of the border have felt serious backlash from large elements of mainstream American society (and with good reason, I might add).
And so you see lots of craven opportunists who elevate themselves to positions of power and prestige by actively working to carve out sections of our society, group them together, and convince them that they are unfairly persecuted and only they, the Anointed Ones, can save them. The irony is, these people require that the people they ostensibly represent continue to suffer in poverty and ignorance; if they somehow elevate themselves, then the opportunists suddenly lose their reason to exist, and their power base.
I'm speaking of people like Jesse Jackson, and a certain 'community organizer' who managed to talk his way into the White House, and people of that ilk.
It truly saddens me that the greatest part of our American heritage, which is the concept of abandoning prior identities and fully embracing America (the whole 'melting pot' thing) has seemingly gone out of style. Now it seems that everybody tries to hyphenate themselves, usually while claiming ongoing persecution and sticking their hand out at the same time.
An interesting exception is the various Asian tribes. While arguably they suffered second-class status for a very long time, their culture and family values led them to seek to elevate themselves through hard work and dedication. This has actually come to work against them--if you are Asian, you will actually be denied admission to certain prestigious universities because of a misguided attempt to 'balance' admissions. Using WASPS as a standard, Asians have to achieve much higher scores to be allowed in, while hispanics and various 'people of color' have much lower standards to meet.
This is the sort of institutionalized racism which is perfectly acceptable to the left-wing liberal elite, ostensibly as payback for unfair treatment to people that were born generations ago. (The fact that Asians suffered this sort of treatment and therefore theoretically should be afforded the same preferential treatment doesn't fit in with their narrative, so they are quietly ignored even as they are discriminated against).
If we were truly a color-blind society, a meritocracy if you will, then the country would look very different indeed. As an advocate for that sort of thing, I find it tragic that we continue to perpetuate racism and discrimination in any form. Having served in the military for the past 23 years (and counting), I am at least isolated from that sort of thing, because the military is truly the most color-blind institution in the country, where advancement is almost solely based on performance, aptitude, and hard work (and, admittedly, a fair amount of ass-kissing at times! :laugh
I really wish that our first non-white President had been Colin Powell. Rather than pitting one group against the other in order to exploit them for his own personal gain, as the Obama crowd does, I truly believe he would have tried to instill the military's merit-based ideology on our country, which definitely would have made it a much better place than it is right now.